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Drop in mileage after oil change

I got my oil changed last week, and filled up my gas tank the next morning. Normally I get about 200 miles on a half tank. This week, I’ve only gotten about 120.

I went to the same service station that I’ve used for the last 6 years. Supposedly they put in high-mileage oil (not synthetic, but not the normal stuff). I also went to the same gas station I normally use. I don’t notice any decrease in performance, no pings or any other change in the car except this.

It could be the high mileage oil, if you don’t usually get that, is responsible for somewhat of a mileage drop, but we don’t know how much of a mileage drop you’ve actually experienced until you fill it up again. Gauging it by when the needle gets to 1/2 tank is wildly inaccurate at best. Tell us the actual mpg you’re getting (and were getting) and we can help you further.

High mileage oil refers to the miles on the car, not its fuel consumption. This oil has some addtives that seal small leaks. Energy Conserving Oil is now standard everywhere, and at most saves 5% in fuel consumption over the old style.

You don’t know your gas mileage until you accurately average 3 or 4 tanks, doing the same kind of driving. In each case record the miles on the odometer at fillp, and again at the next fillup. Subtract the two and divide by the number of gallons. YOU MUST USE THE SAME NOZZLE; within each station, the shutoff time varies quite a bit.

The drop in mileage you appear to have is not due to the oil change, unless they screwed up something on the car. Reading a gas gauge is guaranteed to give you false accuracy.

If the car runs normal, fill it up at THE SAME PUMP, SAME NOZZLE till the first click. Do this for 4 tankfuls if your driving it basically the same. That will give you a half ways accurate answer.

Your driving pattern is the most important variable; stop and go driving in the kind of frigid weather we’ve been having will greatly reduce your mileage.

We get several gas milege questions every week or so. In nearly all cases the driving pattern or the weather are the cause if there was a real decrease.