Hello,
I have a 96 Accord 4 cylinder VTec engine with about 187,000 miles. I previously got around 35-36 mpg which was highway & city driving. About a month ago it went to 31 mpg with the same driving conditions etc. I changed the spark plugs and wires which needed to be done anyway and the rest of the engine's maintenance is pretty well up to date. I will also note that I got new tires around the time this change in gas mileage started. I checked the air pressure in my tires and they all are about 35 psi. Can anybody give me some advice as to why the sudden drop off in mpg?
Thanks.

 

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The car runs as smooth as it ever has. I would have to check my records about the air filter, but it isn't past its due date for a replacement. I do not knowwhen the pcv valve was last replaced.

 

Are the tires/wheels larger than they were before? How are you calculating mpg?

 

The tires are the exact size as before. Rims are original ones that came on vehicle. I calculate the mileage by miles divided by gallons.

 

How many times have you calculated it since the tire change? The reason I ask:right after I installed my SRI I swore my mileage went down by about 4 mpg. Then I waited till I filled up a few more times. The mpg went back up again. It all depends on the gas pump you use. Some pumps will shut off before others.
Unless you use the exact same pump at the exact same gas station every time. The only thing about that is, the same pump may not even cut off at the same "full" level every time.

 

31 mpg sounds really good for honest combined mileage calculated over several tanks. 35-36 sounds bogus to me. maybe all downhill driving?

 

35-36 mpg is acheivable.... I've done it.

 

All miles I drive are to the same destinations etc. I have been driving it a month since the change in mileage. It has just gone down for some reason.

 

Have you been going to the same gas station and using the same pump? Different pumps may cut off at different "fullness" levels producing a false mpg reading.