Can you use regular gas in 2007 Lexus RX 350?

I have just purchased a Lexus Certified Pre-Owned 2007 RX 350. The manual warns that if you use fuel with an octane rating of 91 it could cause serious damage to the engine. We have a Lexus ES 300 that we have run on regular for years. Is this true for the RX? Will it cause damage? Would it void the warranty [30K+ miles left]? Is it possible to use higher octane every 4th tank or some other method to reduce fuel costs? I would like to not damage the vehicle, preserve the warranty, and minimize fuel costs… Any chance of doing all that?

OOPS! I meant an octane rating less than 91.

'The manual warns that if you use fuel with an octane rating of 91 it could cause serious damage to the engine."
You answered your own question.


What does the manual for your ES 300 say regarding octane rating for fuel? All Lexus models are not created equal. If you use regular in your RX 350 and the engine is damaged as a result of low octane fuel (like valve damage, or a hole in a piston) then you would not get warranty coverage for the repair.

Regular is 87 and plus is 89, so you car is supposed to get premium. Use lower octane if you like to take risks.

If you spent so much money for a high-end SUV, why worry about spending a few extra cents a gallon for premium?

The fellas that wrote the manual took the information directly from the design specification package that came from the design engineers. They know the needs of your engine at a level that the rest of us can only imagine. If they say to use premium or you could seriously damage the engine, you’d be foolish to believe anyone who tells you otherwise. That includes us.

1 Like

Manual rules, you have a warranty to maintain, as confused as I am by the same engine using regular in a Camry…I just don’t get it…

Perhaps they’re running a wee bit hotter plug to eliminate that extra 2 molecules of CO.

The truth is the dealer will never know what fuel you put in.

As far as damage maybe or maybe not.

As far as increased cost it is meager $0.20/gallon more in my locale. You are talking around $100+/year extra in fuel costs assuming around 15k per year and 25 MPG.

Wait until the tank is almost empty. Put 5 gallons of 87 octane regular in it and see how it runs…If you can not DETECT any ping or spark knock, you are not doing any engine damage. Damaging detonation is VERY audible. You WILL hear it upon medium to hard acceleration. If you hear nothing, then “serious engine damage” is not going to happen. If you DO hear the engine complain, fill it with Premium and bite the bullet…

I have never seen an “Unleaded Fuel Only” engine damaged by too low octane. 4 or 5 octane points is not enough difference to cause any real damage…An annoying ping, yes. A hole punched in the top of a piston, no…


I think that the best way to minimize fuel cost is to keep up with maintenance and check the tire pressure weekly. Keep the tire pressure at or very slightly above the recommended level (1 to 2 PSI over). Also, don’t carry unnecessary weight. Other than that, I’d buy the premium gas and drive.

First, I want to know why you would buy cars as nice and expensive as a Lexus RX 350 and be cheap about what you feed it. Why didn’t you just buy a little economy car if you are that frugal?

Your RX 350 requires high octane fuel because it has a high compression engine. The fact that it has a high compression engine means you get more performance from your engine (not necessarily better fuel economy), but only when you use the correct fuel, which makes it worth the extra cost.

Don’t be penny wise and pound foolish. If you are that frugal about your fuel, trade in this vehicle for something that uses cheaper gas. You probably won’t actually save any money, but you seem more concerned about your fuel expenses than you do your automotive purchase expenses, which seems totally backwards to me.

I have seen the effects of using 87 octane where 91 was required A Lightning pickup (5.4L Supercharged) was in the shop at the Ford dealership where I once worked. The customer was irrate because he was being denied warranty coverage when a hole did indeed form on the top of piston. He had been using 87 octane, and he paid the price for it.

I will say that in this particular case since the same engine is used in other Toyota products that only spec 87 octane, the OP would probably be okay to use 87 octane. If you look here

and look at page 399. It states “If premium gasoline is not available
If 91 rating gasoline cannot be obtained, you may use unleaded gasoline with an
octane rating as low as 87 (Research Octane Number 91).”

So you can indeed us 87 octane the 2007 Lexus RX350. Whether or not it’s worth the trade off in power and fuel economy is up to you. It’s not like you’ll be saving any huge sums of money using 87 octane vs. 91 octane. If you have a warranty I would use 91 octane until it expires.

1 Like

If you need to risk engine damage to save a few bucks on fuel, you should be in the market for a Toyota and not a Lexus.

Read what the guys say about this here on their site:

That’s the kind of wording my ES300 has, so I’m now wondering - OP, did you quote us exactly what your manual says?

Thank you, thank you.

"Using regular gas in a car designed for premium will definitely damage the engine.

We don’t believe that any modern engine that claims to require premium will be damaged by using regular unleaded judiciously. Neither do any of the sources we’ve checked with ? including the American Petroleum Institute, the American Engine Rebuilders Association ? even a chemist (who would rather go unnamed) at a major gasoline company."

Make sure you read this part (I added emphasis):

I will void my warranty if my owner’s manual calls for premium and I use regular unleaded.

You might, but we don’t think so.

But, that’s just our humble opinion. If you use regular instead of premium, and your car calls for premium, there’s no way we can guarantee that your dealer won’t try to sneak away from taking responsibility for repairs.

But, if we had a vehicle that called for premium, we’d take the risk. There’s a big price difference between regular and premium. That adds up to quite a bit of money over the life of your car.

As a last ditch effort, print out this feature and show it to the dealer. Maybe he’ll come to his senses. But don’t hold your breath.

Tom and Ray fail to make the distinction between cars that recommend high octane fuel and cars that require high octane fuel. Based on what you have told us, your car seems to require high octane fuel.

Tom and Ray are pretty smart, but their advice in this case is generic, and may not apply to your situation.