danielTRLK

When you test these engines routinely you see the differences are vast between running regular and premium. Wear and deposits decrease as the combustion efficiency rises. The reasons stated above are the actual reasons. That was the primary responsibility of my job for a long time and have tested thousands of Toyota/Lexus engines. Humans can not quantify what machines can, it's just not in our ability.

Just like some people say they can feel the effects of gluten free food and then some say it's a bunch of junk.

To the engineering remark. Again, it has more to do with luxury and reliability rather than will it run on regular grade.

MX5NES350

I have run regular in all my cars (Jaguars, Lexus, BMW's, BMW MINIs and never had problems well over 100K. Again my personal experience and YMMV.

17gx460

My 2008 GX470 has 113K miles. Always used regular with no issues. We now also have a 2017 GX460 and we use premium or mid grade although I think my wife typically fills it with regular (87).

I don't think you will see or feel much of a difference. Premium has more cleaning additives so thats a plus but again never been an issue for the GX470 of ours.

The ECU will retard timing when it detects detonation. So with regular you may not get the full power of the car, but who is running these trucks at WOT at the power peak anyway?

Craigyyy

As said above, detergent-wise you don't have anything to worry about if you're buying top-tier gasoline, regular, mid grade or premium.

If it makes you feel better, you can also run a bottle of Techron fuel system cleaner through your tank once a year or so. They're about $5/bottle.

If Toyota wanted us to run premium so we'd get more detergents, they would specify "top tier" on the label too. "Regular" octane gasoline from a top-tier brand is going to have more detergents and cleaning properties than "premium" octane from a discount or nonbranded station.

bbqsoup

I usually buy a box from Costco and use them in all the cars that use 87 twice a yeah, once around Memorial weekend and once around Thanks Giving

jjscsix

Statman

There are a number of posts that discuss the engine being "the same" as in other Toyota products. It doesn't matter whether the engine is the same in terms of using a higher octane fuel. What matters is the programming in the ECU. Timing, AFR, etc. determine the need (or not) for higher octane fuel. Of course, if you use a fuel that has lower octane than the programming requires, the ECU will pull timing to adjust (at what cost????) to prevent pre-mature detonation.

Tessie

I'm a 2-year GX460 owner. I bought it without knowing that I was supposed to use "premium". I followed manufacture guidelines for the first year, and then, accidentally without thinking, put "regular" in the tank. I noticed no difference. I rotated gas tank fillings paying close attention to performance. I couldn't tell the difference. The computer supposed to make necessary adjustments, according to other forum posts. I'm no expert, but if I was pulling a heavy load, I'd fill with premium, otherwise, for highway/around town, I'm using regular. I'm not an octane snob, but am a mechanical engineer. I can understand reduced mpg. I can understand reduced horsepower. But with today's computer technology dominating the vehicles fuel and electronic systems, someone please explain/prove engine damage to me. I'm gratefully open to changing my fill-ups if needed.

simer86

Yeah, Its gonna be my first fuel fillup today since I got my beast a week ago and going by all the views of you experts and my calculations - I would be spending around $500 more on premium per year than regular. So overall my 10 year ownership will make it $5000 if I drive 12000 miles an year.

bbqsoup

Craigyyy

Yeah if premium was just .20 or .30 more per gallon around here I would be more prone to just fill with 93. At some stations though for me it might mean $20.00 more for a tank of gas prem vs regular.

But even $250.00 a year adds up!! Can you tell I'm a cheapskate??

Definitely give it a try and report back. Drive extra smooth and keep it under 55 so you don't throw off the results.

danielTRLK

This field is not quite process engineering, which mechanical engineers really like.

When you use 87, the timing operation becomes retarded, something it appears everyone here agrees to. When timing becomes retarded the engine becomes less efficient. As the engine becomes less efficient fuel dilution becomes more present.

Gasoline is more corrosive than ethanol. This has been proven in too many studies and I've proved it to others in clublexus. In turn the fuel dilution eats up the engine, creates polarized deposits because now we've slowed down the timing so the engine mimics EGR function with valve timing.

So what we have is an engine that will wear pistons, cylinder wall and internals at a faster rate. Not something within 100,000 miles that will blow up your engine, BUT, things that automotive engineers can measure and quantify. Things that will cause an engine to feel rough and unbalanced. If you're used to driving in something you really won't notice the change since it's over time and not drastic. But drive a new vehicle and then one with a 100,000 miles and you can feel the difference.

2. Someone keeps mentioning Top Tier gas. Top Tier gas really only applies to regular grade fuel, Premium fuel for the last ten years from all the big brands have been exceeding the low and crappy Top Tier standard. Also, an OEM will never mandate you fill up with a certain brand, that would be a legal nightmare for whomever should do that. Top Tier is a marketing gimmick by the oil companies meant to confuse the consumer, if Americans saw what synthetic fuels would achieve, the oil companies would be under heavy fire. As a side note and example, Shell, BP, Mobil, Chevron, C-Phillips do not use the same amount and quality additives and detergents in their regular, mid and premium grade fuels. I previously tested for Texas, California and New York DOA to name a few. When you test for any DOA, you're testing the entire states gas stations, so you get to see what's really happening with fuels at the pumps, which is typically the end point before it enters a consumers vehicle.

For the GX guys I have something I believe many will like. I will be testing the vehicle with different grades of fuel, and more neat things like oil filters, different oils, air filters, etc.

Black16

danielTRLK, are you testing different brands of fuel as well or do you typically stick to one or two?

I live in a refinery heavy area... Sunoco, PBF, Phillips, Valero, Chevron, Hess so fuel is relatively inexpensive around me so I dont mind paying for premium. Problem is, I never know who to buy it from. I'm pretty sure PBF supplies all the garbage gas in the area like Wawa, Giant, and the no name brands.

danielTRLK

I only fill up with Shell or Mobil. In my area (Chicagoland suburbs), Mobil has the best 87 and Shell spanks everyone with the 93 V-power.

For the sake of comparison and costs. I will be using just Shell branded fuel for now. I just switched the engine over to 87 octane, will do 10,000 miles, take a sample and repeat the process. Hopefully testing E85 eventually. I will likely skip testing 89 or mid grade for times sake.

Each 10,000 mile set will start with fresh air and oil filter, using the same oil and best attempt at same brand fuel. I'll take the oil sample at the end of the interval, switch over to the new octane for 300 miles and then restart the test cycle. This will allow the engine to start the new cycle as if it had been run on the fuel the entire duration, that way there will be no questions as to whether the new set started out with the computer having to relearn KCLV values, etc.

jjscsix