Camden

I put premium in my MB as the savings are really a small amount compared to the car's price. Also I think that's what I was told. For the GX, my wife - who knows zero about autos - just wants to copy me and thus puts preumium in the GX. As long as I see discrepancies b/w the website and the manual we'll just take the safe route.

bunka

Your statement contradics yourself. The "Proof" you offer indicates that 87 or higher. Regular unleaded IS 87 so it meets that stipulation. Ergo, premium (or even mid-grade) is not REQUIRED but rather is recommended. I am all one for putting in premium where designated (i.e. my TL gets better fuel economy and performance on Premium than on regular). However, studies that demonstrated that there is NO benefit to using premium fuel when the vehicle has been designed to make the best use of 87 octane.

Gohawks63

The fact that you mentioned that your friend was impressed with the accleration and you wrapped up with the fact that you use 87 octane, led to my response that the two have nothing to do with eeach other.

gs400jon

Oh, OK. I should have put that on another line since my intent was just to say 87 octane is what my truck has been running on. Sorry.

Gohawks63

No apologies necessary.

<VENOM>

I run 87 and if I get an 05 GX I'll run that on 87 but for kicks I'll try 93 to see the difference

Gohawks63

You will not experience a noticeable change.... at least not initially.

When running 87 octane in a car designed for 91, nothing may happen initially. But if there is engine knock, the cars onboard computer will gradually retard the timing to eliminate the knock. It may be so gradual and so subtle, you may not even notice it. At least not something you will notice on a tankful of gas.

Another person posted a pretty good response to this same question on another site. I cut & pasted it here.


Most cars today that require premium fuel also have anti knock sensors. Basically it listens for knock and if/when detected it will retard ignition timing to a safe level to prevent the knock that could cause serious engine damage. Retarding ignition timing does cause a loss of power. Using premium fuel will insure that an engine that requires it does not knock and does not activate the anti knock system thus ensuring maximum power potential. It is not the premium fuel that is giving you more power but premium fuel that is allowing your engine to run without a retarded ignition timing.

<VENOM>

I run 10-20 tanks on premium, probably about 2-3 months of hard driving, but I always go by the owners manual and if they say 87 is OK but higher octane for increased performance and I get no increased performance then I'll stick with 87.

With 93 I got worse gas mileage and only managed to visit the gas station more often, maybe your suppost to be light footed but mine hits redline every chance I get once the thing hit the operating temp.

bunka

True for a car/truck DESIGNED to run 91. This truck is DESIGNED to run on 87 octane. The only thing using higher grade does is burn fuel quicker (ala the reason you get the poorer fuel economy by using premium in this truck).

<VENOM>

bunka
have you ever put regular in any of those cars in your sig, mainly the 740 and the AMG

bunka

No WAY I would try it on the AMG but did try it with mid-grade on the Beemer. It did knock slightly initially but it went away quickly. The ignition was retarded as was the fuel econo. Nor would I try it on the Acura. Here's someone else backing up my statements...(From edmunds GX470 forum)

"Money Magazine is absolutely wrong in their statement:

"What it won't do, according to scientists, engineers, and oil companies, is make your car run better, go noticeably faster, last longer, or burn less fuel."

It probably doesn't take a rocket scientist to figure this out, but just in case, I am one. As well as a pilot and current and past owner of high performance cars. Mr. Ulrich, with all due respect, is probably barely qualified to do an oil change, based upon his blanket statment.

It may be true that a few vehicles that are labeled as requiring premium gas may have little or no performance benefits. But there are clear benefits in performance that come from optimally maximizing the energy content of gas by virtue of improved airflow, higher compression and a host of other fine tuning technologies. Yes, because of some penny wise and pound foolish purchasers out there, most of the manufacturers include detectors that will adjust timing so as not to actually result in engine daqmaqge if a lower octane gas is used and the result might have been early detonation and knocking.

Use of lower octane gas is most likely to have a noticable affect on high performance engines that get the most hp out of small displacment. Ferrari, BMW "M" engines (I now own an M5), Honda S2000, some AMG engines are examples. Our 4 year old LX470 would be more difficult to detect, since it's not exactly eeking the most out of a 4.7 liter V8. The new GX470 engine, with variable valve technology, would likely have a more noticable affect.

My advice is not to get suckered into a blanket statement by some moron from Money Magazine. They may be good at advising which mutual fund to buy next year, but I wouldn't give them even a passing mark on engineering intelligence. "

Woogie

91 or 92 octane

bunka

Huh? 81 or 92 WHAT?

Camden

Good info. I may have my wife stop putting 93 in the GX. Does anyone think there'll be a short term effect of going down in octane? Pls excuse the lack of knowledge.

Rx900

I don't know about Lexus, but in a previous car i had, going down from 91 to 87 caused an engine ping, whatever the hell that is, but that's what they said about that car.