A couple of years ago the MPG gradually dropped from 49 to 42, now in the last couple of months it dropped to 36mpg. I changed the spark plugs a year ago, and again two weeks ago. The tips were quite white, but with the new plugs the MPG improved back to 42 MPG, but a week later it is back down to 37 MPG.
Mechanic blamed it on Ethanol gasoline, but EVERY station only sells that, and doesnt quite explain it. I've used it for years.
I think it might be a fuel pump, as I read that could be the problem.
Is there a code reader that will tell me that is the problem, do I just change it and see if that solves it?
What else should I check??
The tips were quite white,
white deposits means they're running too hot, which can happen when the engine runs too lean
Is there a code reader that will tell me that is the problem,
no. code readers are not magic bullets that tell you which parts to replace. But they are useful diagnostic aids which get you closer to the answer with the right experience.
I think it might be a fuel pump
A bad pump is a possibility. You can test your theory with pressure gauge.
do I just change it and see if that solves it?
what if it doesn't? How much money do you want to waste guessing, before you decide to troubleshoot properly?
