Okay to use Unleaded?

[Mailorder]

My '94 Infiniti Q45 has 160,000 miles on it. Bought it used a few years ago, and the previous owner claims he's only used premium gas, so I followed his advice on continuing to use premium.

However, I plan to replace to Q45 within a year. It's currently my daily driver and the miles per gallon is really killing me. Even if I can save a few bucks by filling up with unleaded... I'll do it. How damaging is it to the Q45 if I switch to unleaded?

[BadQ45t]

With that amout of mileage on the car I would say it is a bad move. The car first off will get worse gas mileage so you will not save very much. This could also kill things like knock sensors and other parts.

We've had people post here that either accidentally put in regular or had no choice and had issues....if it was a brand new car on lease, than what the heck, nothing to lose right, but with 160k and a 1st gen I'd personally say keep putting in the expensive stuff.

[Skibane]

Yep, the car will make less power on regular unleaded - which means that you'll have to give it more throttle to make up for the power loss - which means that you could easily end spending more on extra gas than you save by using the low-grade stuff.

What kind of driving are you doing (city, highway, long or short trips, etc.), and what kind of gas mileage are you currently getting?

[elwesso]

Technically they have to design the car for areas that dont get premium or for people that think "premium fuel required" doesnt apply to them. If you want to run regular you can and you wont hurt the car assuming that the car runs good...

Running regular on a Q is like using a golf club without a grip or having a computer without a mouse or keyboard. you have a nice piece of equipment but it takes other equipment to operate it properly.... Whenever someone asks about running regular in a Q I usually turn them to the honda or toyota camry forums...

[maxnix]

However, I plan to replace to Q45 within a year. It's currently my daily driver and the miles per gallon is really killing me. Even if I can save a few bucks by filling up with unleaded... I'll do it. How damaging is it to the Q45 if I switch to unleaded?

Running your VH45DE on regular will cause the timing to retard and you will have a runaway overheat condition in AZ summer, especially if cooling system is not in top as new condition.

Do the math and see how little you will save buying regular vs. premium, or even buying a Honda and burning regular. If you must, ride the bus, bicycle or walk one day a week, or sell the car now.

All legal gasolines are unleaded. Just bad marketing to call the lower grade by that name.

[bullittandy]

[QUOTE=maxnix]Running your VH45DE on regular will cause the timing to retard and you will have a runaway overheat condition in AZ summer, especially if cooling system is not in top as new condition.

QUOTE]

I think you're going crazy. Unleaded fuel causes the car to overheat catastrophically?!?

The car requires 91 Octane. If you have 93 octane in your area then a good way to save money and make the car run the best it can is to fill with 93 octane, use 1/2 tank, then fill with 89 octane and so on and so on.

This also keeps you with a 1/2 tank of fuel which is good fuel pump maintainence.

[96Qowner]

The simple answer is that it's not ok to use 89 octane in the Q45.

[maxnix]

I think you're going crazy. Unleaded fuel causes the car to overheat catastrophically?!?

You need to read more of Q45tech's posts about ignition retardation and it's effect on impaired cooling systems on hot days. Runaway overheat is very easy to achieve on a Q45 with less than optimal cooling system and severe timing retardation caused by low octane.

You know, Q45tech is not far away from you. You ought to go have a conversation with him sometime. But if he has to repeat everything he has posted multiple time, my bet is it will be a very brief one.

[Haitian_King]

damn.

I haven't put a drop of anything but regular in my Q since I bought it January.

F-Word.

I didn't think it would be too bad, I really can't complain about performance. It's fast as all outdoors. The only thing i have is a little bucking once i hit 40mph. Once it hits 60, smooth as a baby's bum.

[bullittandy]

You need to read more of Q45tech's posts about ignition retardation and it's effect on impaired cooling systems on hot days. Runaway overheat is very easy to achieve on a Q45 with less than optimal cooling system and severe timing retardation caused by low octane.

You know, Q45tech is not far away from you. You ought to go have a conversation with him sometime. But if he has to repeat everything he has posted multiple time, my bet is it will be a very brief one.

Why don't YOU explain it?

Do you know what effects retarding the ignition system has on engine performance?

Prove me wrong though, YOU explain to me how retarding the ignition causes a car to "runaway overheat."

[Haitian_King]

Them's sound like fightin' words.

[q45vh]

its it okay to use midgrade on the Q45?!?!?!?! i have a 92 Q

[elwesso]

Midgrade doesnt make any sense to me, i dont konw why they have it. Its like you're too cool for regular, but not cool enough for premium. So mediocre.

[maxnix]

its it okay to use midgrade on the Q45?!?!?!?! i have a 92 Q

RTFSM.

Premium means Premium. Not mid-grade, not regular, not diesel, not kerosene.

[xerexabante]

Using regular specially on hot weather makes the engine work harder. You will have ping. When you have ping it might resault to over heating, and valve damage.

When you have an overheat on your motor what do you hear ahh yes ping. It means your motor is having a hard time running.

[Jesda]

its it okay to use midgrade on the Q45?!?!?!?! i have a 92 Q

NO, and if you do I will hunt you down.

[bullittandy]

I saw this thread again and thought it got resurrected from 1975.

Hey Maxnix, you never did explain how 87 octane fuel causes a "runaway overheat" condition. Why is that?

[maxnix]

Hey Maxnix, you never did explain how 87 octane fuel causes a "runaway overheat" condition. Why is that?

I don't spoon feed the intellectually lazy and studiously ignorant. Too many voluntarily starving dead brains out there.

Here's a hint - what happens thermodynamically when when ignition is retarded? It's all in Q45tech's posts.

"You can lead a whore to culture but you can't make her think." - Dorothy Parker

[Jesda]

I don't spoon feed the intellectually lazy and studiously ignorant. Too many voluntarily starving dead brains out there.

Here's a hint - what happens thermodynamically when when ignition is retarded? It's all in Q45tech's posts.

Wow, you're being kind of a d!ck today!

[superuber]

Must be the heat.

I'm running full cam2 at $6.89 a gallon.

[qship96]

I think if your knock sensors are not working you can run regular gas as the timing is already greatly retarded

[ScottJackson]

I never use mid grade. I use the 87 octane! Yes, it lacks power when you punch the gas, but that's what ya get. At low throttle angles and low load (cruising on relatively flat roads) you're not filling the cylinders much and that means your running compression is quite low. In that instance, low octane doesn't hurt a thing. I get approx 22-24mpg with 87 or 91 octane. I never use ethanol as I don't like replacing injectors. My timing is 18* initial so I think that helps with the miles per gallon. Usually I put in a mix of 87 and 91 octane. If I'm anticipating a long drive of just cruising on open road, I go with 87. If not, I put in 91. For around town or high speed, 91 is a must. That's when you're filling the cylinders with air and you need the detonation resistance of premium. Oh, and I've never had any sort of overheating issue, but it rarely gets above 95* here. The price difference really isn't much between 91 and 87, but I sometimes can't resist the temptation to save a few bucks because even then I only get 6 gallons for my $20

[StarPD]

The simple answer is that it's not ok to use 89 octane in the Q45.

Agreed. Too low of an octane rating (Octane rating is a marker of resistance to detonation, not an indicators of "power") will cause an engine to work harder, and can cause excessive engine heat due to inaudible or even audible detonation.

Detonation (ping) is when their is too much ignition timing advance (for the fuel) and/or too low of an octane rating in the fuel, or if the engine is running too hot. The fuel doesn't burn rapidly, but rather, self-explodes. Even when inaudible, it can eventually knock holes in pistons, break rings, and burn or even break valves. Hard acceleration and/or climbing grades with the A/C on in hot weather can greatly exaggerate this condition, and eventually destroy the engine.

Engines designed for lower octane fuels have lower compression ratios, different cam timing, and different ignition timing curves. They are usually found in lower priced and economy type cars, and usually have lower HP ratings than similar higher HP versions of same displacement and even sometimes the same basic engines.

Using under 91 octane fuel in a Q45 is false economy, and dangerous to an engine like the one in Q45s. For the usual $.20 per gallon price difference, a completel fillup of 22 gallons will cost $4.40 more with Premium than with regular unleaded. That''s a complete fillup from empty. If you fill up completely once a week, that's around $17 a month. Even if you only get 16 MPG, that's enough for 352 miles per week, or 50 miles per day. If you drive that much, you should be able to afford the extra $4.40 per week, or $17 per month. No offense, but if you must count pennies that closely, you need an economy car like my wife's 2000 Ford Focus, which gets 32 MPG on regular, not a Q 45.

[qship96]

I agree with using premium gas,except for the g50 models without functioning knock sensors,as the timing is already greatly retarded below the regular gas grade mode-using premium is awaste until you fix the knock sensors!

[Haitian_King]

How do you know if your knock sensor is malfunctioning...

Sorry that I cant use proper punctuation, Im in Canada and using a Frecnh-Canadian Keyboard. The keys are strange to me. LOL

[Chaluska]

I use unleaded in the Q, ive done extensive testing (1998) I dont know if having an OBD-II makes any difference, i doubt it.

But with a full tank of 93 octane, it drives the same, at every speed as with 87 octane. under WOT i dont hear any pinging, i dont hear any knocking. I never have overheating issues either, and im in humid houston TX.

But i am not saying to use it, i still use Shell V-power 93... but unleaded didnt hurt me at all.. Kept the 16.6 mpg also with unleaded and preminum

[bullittandy]

Hey Maxnix, you never did explain how 87 octane fuel causes a "runaway overheat" condition. Why is that?

I don't spoon feed the intellectually lazy and studiously ignorant. Too many voluntarily starving dead brains out there.

Translation- You don't know.

It's alright though, I don't know alot of things either. However, I also have the ability to say "I don't know." You should say it too, you'll be alot more credible, especially as there are so many things that you DO know about Q45's.

[qship96]

how were your knock sensors during your test? the only way running regular unleaded without a noticable difference is if bad knock sensors have already retarded the timing as far as I know

[StarPD]

I use unleaded in the Q, ive done extensive testing (1998) I dont know if having an OBD-II makes any difference, i doubt it.

But with a full tank of 93 octane, it drives the same, at every speed as with 87 octane. under WOT i dont hear any pinging, i dont hear any knocking. I never have overheating issues either, and im in humid houston TX.

But i am not saying to use it, i still use Shell V-power 93... but unleaded didnt hurt me at all.. Kept the 16.6 mpg also with unleaded and preminum

I'd be interested in Q45tech's take on this.

Personally, I suspect also that knock sensors are not functioning in this case. Science is science, and it won't be denied.

[maxnix]

Hey Maxnix, you never did explain how 87 octane fuel causes a "runaway overheat" condition. Why is that?

Because you are too lazy to find the post and too stupid to follow a hint.