Regular fuel used Lexus rx350

I was told by dealer and gm when I bought my new 2009 Lexus 350 that I could use regular fuel , now 5 years later they’re telling me that I should have used premium. Didn’t I see the recommended premium use label? I am replacing spark plugs, ignition coils, fuel injectors, etc., all at dealer prices. When the mechanic asked me if I had been using regular gas I came unglued. Of course I’m a single woman and of course I believed what I’d been told. My defense is I believed the Lexus reputation. What should I’d do?


You should believe the owner’s manual over what those yahoos told you when you bought the car

That was page 70 from the 2009 Lexus RX350 owner’s manual

The good news is that the engine control module can make allowances for lower grade fuels, up to a point

So, no harm was done. You probably got a little less power from your engine, by using regular.

But use premium from now on

By the way, WHY is the dealer replacing injectors, coils, etc.?

How many miles on the vehicle?

Check engine light on?

Does the engine knock? If not, why are you replacing so much equipment? Since they don’t seem to think they told you about regular gas as a replacement, about all you can do is never go back to them again for service or to buy a car.

You did not believe the Lexus reputation. You believed the car salesman.
Lexus told you via the owner’s manual that you need to use premium. The salesman lied. That’s how some salesmen sell cars. They lie.

Like Db, I too wonder what your symptoms are.
I also wonder why you’re still taking a 2009 to the dealer. You’ll pay far more there and may even get screwed.

Thank you guys for your good comments. I have 68000 miles. The check engine light was on and o’reillys diagnostics said fifth cylinder was misfiring. So then I looked for good mechanic shop by asking people I know. I live in anchorage Alaska. So if you have suggestions/ I know I’m paying for it and don’t like the syrup that the dealer dishes out. I should have paid attention to the manual, but also in my defense, I had an Audi quattro 4 for 15 years and used regular and every third tank put techron in it. Do you think that would work as well now? Also, I’ve noticed that 2014 Lexus 350 can use regular. I’m going to sell this privately. What should I buy that can go through ice and snow as well?

Ignition coil failures are common on the RX350/ES350, this has nothing to do with the grade of fuel you are using. The need for new fuel injectors is questionable.

No, it would not. Techron is an engine cleaner. What you need is the proper octane. They’re totally unrelated. Clean internals keep an engine running properly, but they do not affect the detonation characteristics of the gasoline. That’s controlled by using the correct octane rating.

By the way, modern gasolines contain detergents that render cleaning additives such as Techron unnecessary… at least in the “lower 48”.

Use what the owner’s manual recommends. Trying to take shortcuts to save money will cost you more in the long run than you’ll save.

Sounds like you know and I appreciate it and will use premium now. Thanks.

I was wondering about the ignition coil failure being common. The mechanic said he couldn’t “warranty/guarantee” the work unless he could replace the fuel injector. This was after he tested after being left overnight cold.

The ignition coil failure is totally unrelated to the gasoline used, however it I would not consider it an indication of any causative problem on a vehicle with 68,000 miles, just a routine parts failure. The reason he would not guarantee the work unless he could change the injector too is because both cause misfires, and it’s impossible to guarantee one’s work unless both factors causal to misfires are repaired. An injector misfiring will show up as an ignition misfire, and while injectors can be bench tested, it’s cheaper to just replace them. The shop time to set up and do the test can be more expensive than a new injector.

Many would even suggest replacing all the coils (you have one on each sparkplug), and if you had more mileage I would too, but this is a bit early IMHO for that recommendation. If, however, a second cylinder starts misfiring within the next six months, I’d replace them all.

I see about one ignition coil failure each month on these cars. I have not replaced an injector in the last five years. You must have a very unusual problem or your mechanic inexperienced and not saving you money.

Replacing an ignition coil on the rear bank (cylinders 1,3,5) is about 2 hours labor and $120 for an OEM coil. Add 1/2 an hour to replace the spark plugs.

I think you need to move up here. Between you and mountain bike, you guys could make a fortune. I agreed to pay $722. For $100 per hour labor and parts. They told me that they’re going to see what deal they can make with fuel injector cost at 632.


If I were you, I’d replace #5 coil and plug

If the problem is resolved, forget those injectors

The mechanic thought he should. He had replaced the coil and plug and tested it cold and was still misfiring or so he said. I heard it through the service manager.

So, ok, it sounds like a good idea for db4690 to join in the new mechanics shop in Anchorage. How big do you guys want to make it?

No damage was done using regular in my opinion. This is the same V6 engine that is in millions of Camrys, Highlanders, Venzas, etc, all of which run fine on regular. You’ll get a little more power and fuel economy with premium. I tested both in my Lexus ES300, and found no difference. We’ve had it for 18 years, no problems.

I’ll bet the mechanic would be thrilled if even 20% of that $722 were net profit.
Between the cost of the facilities (complete with compressed air lines, lifts, sufficient power for welders, etc.), the cost of dealing with the hazardous materials waste, the many thousands of dollars in tools, insurance, taxes (property and business-profits), “shop supplies” (rags, oil, grease, and other disposables), and heat/lights/water, there aren’t too many mechanics getting wealthy.

Do you have the fault code information from O’reileys? I wonder if he replaced the coil on the correct cylinder.

I will make sure of the mechanic replaced the right coil on Monday. I didn’t get anything in writing from o’reillys though.

You won’t be able to see the coil for cylinder #5, it is under the intake plenum.