Premium vs. lower grade gas?????

[06M35Sport]

I have a 06 M35 sport and I know the M's and I think all of Infiniti products call for Premium fuel only. Sometimes if it tells you that, it really doesnt matter if you use a lower grade gas. For some reason, I think I remember reading something about that here but cant seem to find it. I thought i read that members here reccomended it and said using lower grade fuel messed up the fuel filter or something. Maybe I dreamed that but with fuel cost now days I was just wondering if I was using premium for no reason at all but just because that is what it tells me. Im sure premium is better for the performance of the vehicles, but is there another downfall for using lower grade fuel? Personally, its not that much more to use Premium when filling up and I dont want to sacrifice vehicle issues to save a few bucks at the pump. Just curious if anyone can help me on this. Thanks!

[83wildcat]

I have a M35X and I switched between regular and premium for several months and didn't notice any difference. The car performed the same and there was no change to mpg. I believe that Infiniti "recommends" premium on the M35/M35X, but it isn't required. It's not that much of a difference in cost, but why give it away if you don't need to. I think I'm keeping with regular from now on.

[New2Import]

I dont know about the 35 but the 45 hates 87. Pings its a$$ off. Wife made a mistake and only put in like 3 gallons and it done this. High compression engines need the high octane. You are destroying your engine with detonation if you do this. I dont know the compression of the 35 but if is 10 or higher you bettter put the 92-3 in it.

[EcstaSPT]

I can tell a definite difference between 87 and 93 (06 M45). Especially in hot weather. Our cars have a knock sensor which retards the timing when it senses pinging but like new2 said it can still happen, and is not good.

[jmcclain01]

I use the "cheap" stuff, if that's even possible with today's gas prices, and have not had any issues. I don't drive like a mad man and am very seldomly in the throttle enough to make the engine ping even if it is going to. I don't think anyone on this forum, or that knows cars at all for that matter, will recomend using low octane fuel, the higher octane is always better, but I don't think you'll "destroy" your engine by using 87 octane.

[EniGmA1987]

I can notice a power and milage difference when using lower grade fuel. Not worth it at all to me. If you think about it, you really only save like $2 when using 89 fuel instead of 91. Are you so tight for money that you will try to save $2 and risk your car?

[szh]

Folks, the M45 requires 91. Putting in 87 is certain to lead to silent pinging (that is how the knock sensors do their work after all) and you are hurting your engine with long-term use whether you willing to admit it or not.

It is a false economy to use 87 when the car requires 91 given the current gas price differential. The typical difference in operating cost for using 91 instead of 87 is between $10 to $20 a month for MOST peoples driven miles. If this is truly a big deal, then the owner of the M should really have gotten a different car.

Please note that this is not meant to be an insult at all! It is, indeed, a fact of life that some people perhaps cannot afford this small difference on a long-term basis. For them, buying a car beyond their means is something any financial advisor would be against too.

Another thing to think about: on my wife's Acura 2.2CL, the requirement is 86(!) but I get more mpg (I tested this: there is an old post about it at NICO somewhere) with 91 than 87 and this more than compensates for the price difference - so the cost per mile is lower with 91. It is probably the same with the M45 (although I would never willingly put 87 into it).

Bottom line: the M35 says 87 minimum (and recommends higher), the M45 says 91 minimum. Please use the correct gas for the car.

Z

[bfournier]

I have a 2006 m35x and just recently started putting 91 or 93 regularly and have noticed a difference...specifically acceleration and seems to more responsive

[BigP]

I use only 91 to 93 in my 06 M45. I use about 60 gallons a month so it costs about $15-18 more per month. Even if it did not hurt the engine I'm sure I would lose at least 1 MPG which equates to 3-4 gallons more per month which is about $8-10 loss so the net is about a $10/month saving. Not worth even thinking about given the likely engine damage as mentioned by the experts! I have put regular in several Q45s and you can tell the difference!

[Double E]

AMEN to that Szho.

The wife put the 87 in mine once. Told me about it after I said the M was running poorly & knocking. She doesn't drive it any longer.

[NightWatch]

The M35 doesn't "require" premium fuel but with that said.... I have had to use 87 octane when we had the gas shortage in GA and the car did seem more sluggish - no pinging, but it didn't seem to have as much power either. It also got poorer gas mileage. My commute mileage went from close to 20 MPG down to less than 18 MPG.

But...with that said.... If you drive 15,000 miles a year like me and get about 20 MPG and the cost difference between regular and premium is about 20 cents like it is here in GA.... You're only saving about $150 a year in gas. Now if you can afford to buy a luxury car.... shouldn't you be able to fork out a measley $150 extra a year in gas to make sure its getting gas that it can run efficiently on?

[06M35Sport]

Just reading these posts, it looks like everyone has their own experience with using lower grade fuel. Sounds like the m45 really needs to use the higher octane gas and the m35 could possibly use the middle grade. I guess it does say its reccomended but not required. I have been using the high octane gas and like I said the difference in cost is not that much, but I was just curious if those extra bucks I have been spending were even making a difference. I dont have a problem with the extra cost and from these posts I will continue to use the premium gas. I just dont want to damage anything in the engine. Those extra dollars are worth keeping the engine running great. I knew this going into the purchase and dont have a problem with it. I agree, if I cant afford those extra dollars at the pump a year I dont need to be driving this car. With that said, I appreciate the responses and this answers my question. I will continue to use premium gas.

[szh]

Sounds like the m45 really needs to use the higher octane gas and the m35 could possibly use the middle grade. I guess it does say its reccomended but not required.

Correct - both sentences.

I have been using the high octane gas and like I said the difference in cost is not that much, but I was just curious if those extra bucks I have been spending were even making a difference. I dont have a problem with the extra cost and from these posts I will continue to use the premium gas. I just dont want to damage anything in the engine. Those extra dollars are worth keeping the engine running great. I knew this going into the purchase and dont have a problem with it. I agree, if I cant afford those extra dollars at the pump a year I dont need to be driving this car. With that said, I appreciate the responses and this answers my question. I will continue to use premium gas.

Good Stuff™!

Z

[jwheaton]

I worked out the math and figured I'd only be saving $120-200 per year by using 87 over 91, even though my 2006 M35x doesn't "require" it.

I think it's worth it to me, even if it is all for nothing. I waste $200 a year on way worse stuff than that.

I also use Shell gasoline exclusively (unless I'm stuck) for the "V Power", "Nitrogen", and the fact that they are in that gasoline consortium etc etc. Again may be for nothing, but for what I paid for the car, it is a very very small price to pay.

[Zamba]

I have a 2006 m35x and just recently started putting 91 or 93 regularly and have noticed a difference...specifically acceleration and seems to more responsive

I think I've noticed the same in my m35x but I'm wondering if it's just a placebo effect.

[nordy]

Ive been using Regular in my M35 for over a year now and no difference or pinging in mine, however mine is a daily driver and I drive it easy. Rarely gone anywhere near the red line, that's what the weekend toy is for

[M45Runner]

I think I've noticed the same in my m35x but I'm wondering if it's just a placebo effect.

Yes, they are. If a car does not REQUIRES premium, it will not hurt the car running on 87, but you will feel a difference in performance and at the same time a gain, yes, gain in MPG. since premium gas has less energy than regular, it just has a higher ignition point (for the high compression ratio).

[cobblecanyon]

Like the label on the tank cap opener said....use Premium for best performance. If you don't care how your car drive in terms of cleaner fuel/performance by using Premium, than by all means put in Regular Unleaded. I don't know about most of you but driving with Regular and Premium is a world of difference in terms of performance. There's more pickup with Premium. There is no denying in that.

[EcstaSPT]

Anyone Seafoamed their M yet? I'm thinking about doing it to my end of the month lease turn-in and see how much stuff I burn off and see if there's a SOTP difference. If so I'll do it to the one I just bought

[83wildcat]

I agree, my savings would be about $150/year using 87 octane over 91 octane. Can I afford it - sure. But, I'd rather spend my hard earned $150 on a nice dinner with my wife rather than contributing to the some anonymous oil executive's bonus. It's because I just don't see any difference between 87 and 91 octane on my '06 M35X. If I did, or felt that I was damaging the engine, it would be 91 octane all the time. Sounds like the M45 folks do benefit. Talk to a G37 owner, I think it will void their warranty if they use a lower octane fuel. I do use 91 octane all the time for my Harley. Those cases - yes; for my M35X - no.

[antzrus]

I think I've noticed the same in my m35x but I'm wondering if it's just a placebo effect.

Wise man are you. The '06 M35x does just fine on regular-unless of course you drive near the red line all the time.

Placebo (google it) is a very, very effective way to make your brain literally (actually physically change) feel better about many things, pain, depression and anxiety are just a few. Your precious M35x doesn't know the difference between 87 and 91. But your brain does...

[EniGmA1987]

So the slower 0-60 and especially 0-100 times are just in my head? Thats good to know.

[EcstaSPT]

So the slower 0-60 and especially 0-100 times are just in my head? Thats good to know.

Do you have timeslips showing the difference?

[MinisterofDOOM]

Your precious M35x doesn't know the difference between 87 and 91. But your brain does...

Actually, the M DOES know the difference, and that's what's important. VQ35 will run on anything 87 to 93 (maybe even 85, I've never tried it). But there IS a difference. With 91, the car can operate with optimal timing advance. With 87 it cannot. It makes less power and is slightly less efficient. That's why the engine has knock sensors: to compensate for lower octane fuels. Key word is compensate. It works and is not harmful at all, but is less than ideal. Most modern engines push the limit pretty hard with high compression, so they're very susceptible to knock from low octane fuels. To avoid knock, timing must be retarded and power is lost.

That's just for the VQ, though. The VK45 is a different story as Z already noted above.

[nicom35s]

I used 87 for my M35s and I heard pinging when I rolled down my window and accelerate heavily. Now Im using 91 and so far so good.

[Poyzinous]

There is a lot of misleading info out there. The VQ was designed and built upon 91 octane. Use 87, you WILL experience engine knock and a loss of power. Take your car to a dyno on your 2nd tank of regular. Take it back on a 2nd tank of premium. If the results are unchanged, I'll double the money you spent on the dynos. MPG honestly will only improve .5 to 1 mpg from 87 to 91, depending on driving habits. This is because the ecm will adapt to the crap you're feeding it. The M can run on regular, but there will be spark knock, there not be the 280 Hp you paid for, and you'll just look like a fake paying 50k for a premium vehicle and cheaping out on crap fuel. If you have an HD Television, do you have HD cable or HD tv programming? A HD/bluray dvd player? or do you have your HDTV connected to rabbit ears and wads of aluminum foil and a VHS player?

[antzrus]

There is a lot of misleading info out there. The VQ was designed and built upon 91 octane. Use 87, you WILL experience engine knock and a loss of power. Take your car to a dyno on your 2nd tank of regular. Take it back on a 2nd tank of premium. If the results are unchanged, I'll double the money you spent on the dynos. MPG honestly will only improve .5 to 1 mpg from 87 to 91, depending on driving habits. This is because the ecm will adapt to the crap you're feeding it. The M can run on regular, but there will be spark knock, there not be the 280 Hp you paid for, and you'll just look like a fake paying 50k for a premium vehicle and cheaping out on crap fuel. If you have an HD Television, do you have HD cable or HD tv programming? A HD/bluray dvd player? or do you have your HDTV connected to rabbit ears and wads of aluminum foil and a VHS player?

This issue of 87 vs 91 reminds me of the issue of oil changes, 3000 vs 15000. In all my 46 years of legally putting these rolling objects down the road and when I was saving my pennies putting just about any old viscous oily substance, the cheapest the better and gawd knows how long before changing, I never, ever had a problem w/an engine caused by the oil; even after finding that there was hardly any oil on the dipstick!!!

Come on folks, the degree of pinging and the degree of mileage loss and the degree of horsepower loss @ normal, sane RPMs is not within human sensory perceivable difference as already noted above. You need an especially adept mechanical device to note the difference, not the human central nervous system.

The true difference noted by humanity w/out all these inhumanly precise instruments measuring this and that is as William James in 1890 so aptly stated: "Whilst part of what we perceive comes thru our senses from the object before us, another part (and it may be the larger) always comes out of our own mind."

In my poor perception, the placebos have it.

Geez, guys-what do you think multi million dollar advertising is all about?!!

Oh yeah. When I buy HDMI cables et al, I always go for the cheapest on the internet; no perceivable human difference between the two.

[Poyzinous]

This issue of 87 vs 91 reminds me of the issue of oil changes, 3000 vs 15000. In all my 46 years of legally putting these rolling objects down the road and when I was saving my pennies putting just about any old viscous oily substance, the cheapest the better and gawd knows how long before changing, I never, ever had a problem w/an engine caused by the oil; even after finding that there was hardly any oil on the dipstick!!!

Modern engines have clearances and tolerances that are 2 to 5 times tighter than back in those days. Things are different. Thats why a Chevy 350 could only produce 220 net hp (claimed 300 then) with only 13mpg but a modern 350 can produce 50% more power with 50% better fuel consumption, not to mention it would take 7 of them to be as dirty emissions wise as an old 350. Either way, Being a tech I change my oil every 2500 to 3000 miles just because I can, and when you take a peek inside my engine with 55000 miles, I guaranfreakintee its cleaner than my neighbors 20000 mile accord with 5000 mile jiffy lube reprocessed oil change intervals. The motors on all infinitis can go 5000 miles between changes, but see the v6 only has 5 quarts to go through. The V8 5.7 quarts. 3750 miles is the recommended interval by infiniti because that is where you'll maintain optimum efficiency and life and reliability. You can go 5000 if you want to, but be sure to add a half quart to the motor, since it naturally eats about a tenth quart per 1000 miles, the V8 about 2 tenths. If the M's engine had a 9 quart capacity like some of the other luxury cars that have 7500 mile intervals, then you could brag about 7500 mile intervals between oil changes. Oh, and all i need is to stand within 10 feet of an M, drive it up a slight incline from a dead stop and I'll know if its using regular or premium. I've had to 'diagnose' many cars with a 'pinging' as the issue, only to advise the use of premium, and the customer never have the issue again. A member over at the G forum did a big research graph showing that the fuel economy improvement from premium over regular was worth the variance in cost of fuel when calculated to cents per mile, and you're better off using premium. Especially the more expensive gas gets, since the variance gap closes as the cost increases.

[MinisterofDOOM]

Come on folks, the degree of pinging and the degree of mileage loss and the degree of horsepower loss @ normal, sane RPMs is not within human sensory perceivable difference as already noted above. You need an especially adept mechanical device to note the difference, not the human central nervous system.

The true difference noted by humanity w/out all these inhumanly precise instruments measuring this and that is as William James in 1890 so aptly stated: "Whilst part of what we perceive comes thru our senses from the object before us, another part (and it may be the larger) always comes out of our own mind."

But that's just it...that's what we're telling you. The issue is NOT perception, it's mechanical fact. Just because you can't tell the difference doesn't mean there isn't one. For those looking for a noticable difference, sure, your point may be valid. But there is fact, undeniable fact, science, go ask the engineer who built the motor, that lower octane fuel reduces performance and economy because it forces the engine to operate outside optimal parameters. You can go on about advertising and placebos all you want, but either you don't understand what you're talking about or you're ignoring basic physics. Advertising doesn't change compression or gasoline's knock-resistance.

[M45Runner]

You got a good point - the engineers know how the engine performs and they did NOT say you NEED to use premium gas, just recommended - simply to back up their claimed HP, that's it. So, it is all about advertising / brag rights (for Infiniti). I bet you Infiniti will not decline warranty if you use 87 exclusively if there is anything wrong with the engine. That would be enough to justify using 87 for M35. Since I have the M45, that is a totally different ball game - I use 91 - 93 only for performance, that is why I bought M45, not M35. If I got a M35, I would not waste my money.

I have owned another car that says Premium gas REQUIRED and I have been running on 87 for 150K miles without any engine problem - as a matter of fact, the only problem I had with the car is the front suspension, which is due to struts leakage. When I have the timing belt changed, the mechanic says the engine is in excellent condition and again at 140K miles, I want to do a valve adjustment, they opened it up and inspected and told me it is not needed since everything inside the engine is in excellent condition and still within NEW spec. By the way, I change my oil every 7500 miles. So, that basically proof using Premium when not REQUIRED or change oil more frequently is just a waste of money and all mental thing. It will not make a damn bit difference for reliability. But, if you want to waste your money and burn premium and change oil every 2000 miles, that is OK, it is your money and you can spend it whatever way you want.