Who's the first to put regular octane gas on their GX550? (2 Viewers)

[rgsiii]

I do not have a GX. I have three other Lexus vehicles that call for premium fuel. The LX570 calls for premium and the essentially identical 200 Land Cruiser says regular is fine. I have used regular with the LX, a GS350 and a NX300 after evaluating both regular and premium, I have found no difference in MPG or acceleration.
Will this be the same with the GX?

 

[steveperry]

Now, on the question of whether Regular would actually do any damage to the GX.... Toyota specs Regular for the Tundra, which uses the same engine. So why does the GX need Premium?

I've wondered about that as well. We have a tundra that's happy to run 87. I've wondered if it's something with the tuning or if the turbos are different or what.

 

[killy]

it is well known that the tundra and the GX have different turbos.

It is likely emissions related, running lower octane gas will require more fuel to prevent the AF mixture being too lean and knocking on the more efficient tune.

the cost of premium fuel is offset by the increase in mileage and you get more power to boot.

 

[cloey701]

As someone that's calibrated engines, I would highly recommend against regularly using lower octane fuel. While it's true the ECU has ignition timing and boost tables to compensate for knock and other adverse conditions, you don't want to constantly rely on that to keep the engine safe. This is especially true under higher load conditions like rapid acceleration or towing.

Keep in mind that all else being equal, (e.g. air and coolant temps) the knock sensor(s) have detect knock before the ECU reduces ignition timing. So there's a real chance of premature wear and/or damage if that's regularly happening.

On maximum effort racing applications, "riding the knock sensor" can allow the engine to run closer to MBT but that's not a strategy for a daily driven car where the operational target is 150k+ miles. Can you run lower octane fuel occasionally and get away with? Sure. There's just little reason to do so.

Finally, the GX550 is priced between 65k - 83k. If the small additional cost of premium fuel is too much for your budget, then you bought the wrong car.

Well, I have both the new and old GX. I know the new GX is completely different from the V8 in my 2014, and maybe that’s why I’ve been lucky with regular gas. I have had no issues and I’m at 190,000 mile. The new one is my husbands and does use the premium. I’ll take my risk and continue with the regular. I’ve had it for 10 years and if starts giving problems then I’m fine trading it in, I got my money’s worth anyways

 

[YellowLab]

Only reason the manufacturer recommends premium is to meet their power and mileage claims. You can use regular. Yes their will be less power, hardly noticeable, and yes a little less mileage, hardly noticeable. But the computer will take care of any possible detonation.

You mean it's possible to get worse than 13mpg???

 

[AGP]

Only have 3K miles on ours but in New Mexico. It's sometimes difficult to find >89 octane. I've filled up on that a handful of times and driven to TX no issues. Hard to tell what performance differences it makes since we're at over 8K altitude where I live. So I have a natural handicap. But, so far OK.

 

[killy]

Well high altitude mitigates knock anyway so thats a plus

 

[jdbassman]

doesn't lower octane change the compression ratio?

 

[jclaffee]

doesn't lower octane change the compression ratio?

No

 

[killy]

doesn't lower octane change the compression ratio?

Compression ratio is a physical property of the engine that cannot be easily altered.

A high compression ratio may necessitate a higher octane gasoline, depending on a few other operating parameters of the engine.

 

[JoeRob]

Using regular, 87 octane, should only result in the engine timing backing down a bit when "knocking" is happening. The only differences between premium and regular are the "chemicals" added to premium to raise the octane. Those chemicals are added to the premium gas at the gasoline distribution location when the various brands/sellers of gasoline pick up the bulk gasoline for delivery to the gas stations where gasoline is sold. So, your regular gasoline use should only result in the engine not performing at "its' " best - whatever that is, as the timing of the engine is adjusted to prevent/limit any pre-detonation/pinging. The engine probably won't perform its' best but we probably won't even notice that slight detuning that happens.

 

[killy]

These days higher octane is mostly achieved with higher ethanol content rather than chemical additives. However the base petroleum composition of regular versus premium gasoline is determined at the refinery. Gasoline is a blend of refined products some of which are more volatile and prone to knock than others, with ethanol mandates dictated by the corn lobby in Iowa these days refineries are tuned to produce less valuable sub octane gas that ( say ~85 measured octane for regular and ~90 measured octane for premiums) and blended with ~10% ethanol which has a natural octane rating of 100.

Most gas stations only have 3 tanks on site, one regular, one premium, and one diesel ( though I have seen some retailers try to market a scam known as premium diesel lmao ). Mid grade is just a 50/50 blend of premium and regular.

Premium gasolines may have additional additives as a marketing tool to get more people to buy premium, but they aren’t the primary method of achieving octane rating.

 

[YellowLab]

Please define premium - in the People’s Republic of CA we are only allowed 89 octane at nearly all stations - I've not seen 91 in quite a while. God forbid the chaos to the matrix if they let us have 93....

 

[killy]

Premium is 91 or higher.

89 is mid grade

87 regualar

85 is for the love of god keep driving

I don’t think my other car would even run on 89 lol, it requires 93