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Gasoline choices

The 2010 Lexus rx350 manual says to use Premium gasoline…what happens if I use regular.

The short answer is ENGINE DAMAGE. That’s all you should need to know.

Here’s the long answer:

If you use regular, someone will slap you on the side of the head and say, “Why did you buy an expensive car and feed it cheap fuel?”

If you can’t afford to use premium gasoline, you can’t afford to own a 2010 Lexus rx350. If what you want is cheap fuel, buy yourself a cheap little econobox.

As others will chime in, you will have pre-ignition (pinging) and eventually you will have holes in you pistons and other engine damage. Trying to save a few bucks on a tank of gas does not go very far in replacing a $5000+ Lexus engine.

Luxury cars get higher performance from their engines by higher compression ratios, requiring premium gas. The assumption is that those who can afford a Lexus can also afford to buy to more expensive gas.

Go to your dealer, talk to the service manager, and ask him if he has any engines in his shop that have been damaged by using regular gasoline. If he does, ask to see the damaged parts. This would be a good education for you to see.


The engine will adjust itself resulting potentially in less MPG and/or power. It will also run outside of design parameters and potentially cause damage.

I found in my car requiring premium due to the drop in MPG using regular yields no savings. Also the power loss is noticable but my car is high sprung(WRX).

I addition to the engine damage, it will also reduce your mileage and decrease power. So why would you want to pay good money on a nice car like that then reduce the fuel mileage and power? You could have just bought a cheaper car to start with.

Does it say ‘recommended’, or ‘required’? The engine is the same as used in Camrys and Highlanders, where regular is allowed. I think is says something like ‘premium is recommended for optimum engine performance’. That is not the same as ‘required’. I have used regular in my ES300 for 15 years, still going strong.

You bought a premium car, it needs the premium stuff to run; why skimp on it?
At 19 gallons in the tank, you’re only gonna save, what, $4 per fill up?

In a nutshell, your car will change it’s engine performance parameters to compensate for the lower quality fuel, resulting in lower efficiency, less power, and fewer miles per gallon.

The price difference between regular and premium is about 20 cents per gallon.

Lets say you drive 1200 miles per month, and get 20 mpg. You’ll use 60 gallons of fuel, a price difference of $12/month between premium and regular. Wow.

But with the regular gas you’ll lose efficiency and mileage. Let’s say you only lose 1 mpg. Now you’re using 63 gallons per month. So you’re buying 3 more gallons of fuel. At today’s prices that’s almost $12. You’ll save NOTHING.

Asemaster hit the nail on the head. Switching to regular could easily cost you more money.

Suppose you switch to regular.
With a 5% difference in price between regular and premium, if your car’s mileage is normally 20 mpg and it drops more than 1 mpg, then it’s costing you more.

Some engines are less sensitive to switching to regular than others. Some will suffer more than a 5% drop in mileage, and others less noticeable. But why do it?

Trade in the Lexus for an equivalent Toyota. The Toyota will run fine on regular.

If you keep the Lexus and use regular it is at your own risk. Engine damage, pistons with holes in them, are not a cheap fix.

Trade in the Lexus for an equivalent Toyota. The Toyota will run fine on regular.

The equivalent toyota will also require high octane. They use the exact same engine.

Why spend $40k on a car if you can’t afford premium unleaded? If the manufacturer specifies premium, you need to use premium or risk engine damage. The risks others have mentioned are real, as well as the probability of lost fuel mileage and engine performance. If you don’t want to pay for premium fuel, don’t buy a premium vehicle.