Is low-octane fuel to blame for my car’s problems?

John Paul, AAA Northeast's Car Doctor, answers a question from a reader looking for the cause of a costly repair.

Stephen Morton/Bloomberg

Q. I have a new Mercedes-Benz AMG E 63 and recently lent the car to my brother. When he returned it, he’d washed it and filled the gas tank. After driving the car for a few days, it started to run roughly and the check engine light came on. The dealer told me it was because my brother used regular, not premium 93 octane fuel. The dealer needed to clean out the fuel system and replace all the fuel injectors (at my cost). I don’t blame my brother, but can just one tank of 87 octane fuel cause this much damage?


A. It is important to use premium fuel in cars that require it, but one tank full is not going to cause a problem. Here is what is stated in the AMG owner’s manual: “As a temporary measure, if the recommended fuel is not available, you may also use unleaded regular gasoline.” I believe the issue was not the wrong gas, but contaminated gas. I would go talk with the gas station where your brother filled up. The contamination wouldn’t have affected just your car. I’m sure there are others.

Q. I have a 1974 Chevy Camaro that I’ve owned the last 43 years. It has been sitting idle in a garage for the last 15 years. What are your thoughts on it?


A. The 1974 Chevrolet Camaro is not the most collectable Camaro. Even the most collectible 1974 Z-28 was underpowered compared to other vehicles of the time. Someone I know had almost the same car that sat for just about the same time, and because of sentimental value decided to restore it. Every rubber seal needed replacement, the engine and transmission needed rebuilding, there were rusted-out floors, and the car needed a complete repaint. All of the brake system and steering and suspension parts needed replacement. Plus, the interior was moldy and needed more than cleaning. When it was done it came out great, but realistically, the cost of restoration was twice the value of the car. To me he is going to need to keep it another 40 years to see any return on his investment. At this point I would have your car towed to a restoration shop, have them evaluate the entire car, and give you an idea (and it will only be an idea — there is always hidden damage/rust/mechanical issues) of what it will cost.


Q. I have been hearing about a new small truck from Ford, the Maverick. What do you know of it and what do you think? Is it really “Ford Tough”?

A. I have always been a fan of true compact trucks, and I think there is a market for a somewhat basic truck that can handle day-to-day driving, is easy to park, can handle trips to the home improvement center, and is not outrageously expensive. The Maverick in front-wheel drive (all-wheel drive is optional), with a fuel-efficient hybrid engine will run about $20,000. Regarding “Ford-tough” — time will tell, but Ford is confident this latest Maverick will not disappoint truck fans. I was able to look at a very early production Maverick recently, and based on what I saw, Ford will sell as many as they can make.


Q. We have a 2001 Toyota Corolla with 170,000 miles. It has some minor rust and some city dents, has only one speaker for the radio, and only the AM radio works. Other than that, it’s a perfect car for me, since I like the way it drives. The check engine light has been on for over a year and the car won’t pass inspection next January. Do you think it’s worth having it fixed, or should we just donate the car? If we can get the check engine light off, any thoughts about the radio?

A. I would certainly get an idea what the problem is. At 20 years old and 170,000, the car could be at the end of its life. Since the car runs well, it’s possible the issue is with the evaporative emissions system. It’s very common with Corollas that the purge valve fails. When that system has an issue, the engine will run fine, but the check engine light will be on. Now, of course this is just one possibility. At this point I would want to get a diagnostic check of the car as well as an overall evaluation. If the car looks like it is safe and can be repaired for $500 or so, it may be money well spent. As far as the radio goes, mount a Bluetooth speaker and listen to music from your phone — that’s the cheapest alternative to a new radio and speakers.


John Paul is AAA Northeast’s Car Doctor. He has over 40 years of experience in the automotive business and is an ASE-certified master technician. E-mail your car question to [email protected] Listen to Car Doctor on the radio at 10 a.m. every Saturday on 104.9 FM or online at

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