Premium vs. lower grade gas?????

[NightRiderQ45]

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.

Well said. I change my oil every 5k miles. SM rated oil we have now is far superior to the SH oil that my car was rated for in 98. If I can get 3750 miles out of the SH oil, SM can easily go 5k. Also I've put 87 in my car which requires Premium and off of my last tank, I've actually gotten better mileage out of the 87 than 91.

[antzrus]

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.

Amen. The issue here for us car nutz is that we are especially compulsive (it's all a mind thing) about our machines. Come on now. We spent more than the average for these machines, we communicate regularly herein re them, we baby them and we want not the average, but the best for them. Therefore it just doesn't feel (placebo here) right not doing the best we can for them. There is this human thought (placebo again) that unless we pay a lot for something it is valueless/has no real substance.

Got an M35? Go ahead, play w/your mind, 87 vs 91, see how it feels, try 89 instead!!!

[szh]

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!!!

A change of topic, but ...

My philosophy: if you change the oil often enough, using inexpensive 5W-30 oil is perfectly fine.

If I was forced to make a choice between changing the oil with expensive 5W-30 synthetic at 15k miles and changing the oil with cheap 5W-30 dino oil at 3k miles, I'd pick the 3k low-cost dino oil change every time. Because, in my mind, changing sooner ... to get the collected crap in the oil out of the engine more quickly ... is probably a better idea.

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.

Umm ... not a valid comparison. HDMI is a digital bits transmission, so until the signal quality drops to the point where the error handling can't correct for dropped bits, the outcome is unchanged by full error-correction. Basically a cliff. So, yes, using inexpensive HDMI cable is perfectly fine. It is not the same as analog speaker cables though.

An engine performance with gas changes is "analog". As the gas quality degrades, the engine - particularly when pushed (and who does not push their M hard on occasion? ) - progressively sees more silent pinging and internal inaudible knocking. These are compensated for by the engine management, using the knock sensors, only up to a point. Then these mini off-timed explosions become loud enough to become audible knocking and, yes, they will, to some degree damage the engine in ways that you might not expect. Our engines are prone to carbon build-up for example.

And, during this process, the available power and mileage have been decreasing too - not digitally off a cliff, but with some curve.

My thoughts:

M45:

1. The M45 requires 91 or higher. Use 91 or 93.

2. Don't use 87 or 89.

2. Or change to another car if this $10 to $20 per month extra cost is an issue.

M35:

1. The M35 requires 87 and only recommends higher. Use 87.

2. If you want slightly better performance, or want to avoid the occasional bad gas at some stations , use 89 or 91.

3. Consider testing - over a few tankfuls (without cheating) - to see if 91 gives you better overall mileage for your particular driving patterns and any improvement in "cost per mile". If so, switch to what gives you the best cost/mile.

The reason I say "test" is because of the real-world experience I have noted with my wife's Acura where the requirement is 86, but the actual cost per mile with 91 is measured to be better. As mentioned in a post from me before.

Z