Kyras

Friends, you know I've been on the road for eight days, now, not counting today. I expected to get some 30+ miles per gallon. I'm only getting around 28 mpg, even when I'm only doing about 75 mph. That is not normal for my trips with my '05 S2000. I'm thinking perhaps new spark plugs would help. Any other ideas? The car is running fine and not burning oil.

...I keep records in an autolog book, in which I write down every tank of gas, etc. I only have the second one with me, so I don't know when I replaced the spark plugs. That is I assume I have done it once before now. I'm at 88,000 miles.

A friend of Jerry's gave me a recommendation of a great Honda dealership near tonight's destination, Lawrence, Kansas. I'm thinking of calling ahead to see if he has the plugs on hand and can put them in for me this afternoon.

mns2k

Down here they change the mix of the gas to a summer grade for pollution control. The MPGs always go down when they make the change

Kyras

^Oh! I did notice the signs on the pump about the mixture. Would that really make a 3 to 5 mpg change? I was expecting at least 30 mpg and up to 33 mpg, not 28 mpg.

JonasM

You also have new tires. I would expect the rolling resistance to be higher with new tread, but I don't know if it would be enough to make that big of a difference.

JonasM

Bass

88k might be a good time to swap the plugs BUT also how's your air filter?

Tadashi

Normally it's 90K recommended for Honda plug replacement. Agree with Steve about the air filter, I do mine every 15K!

Top down driving gets way worse mileage than top up.

If your tires are inflated lower than the old ones that could make a difference as well. My Civics were under-inflated and cost me 4 mpg!

Glad I am not the only "Cork" who keeps a log book about mileage and stuff

HannibalACP82

What everyone else said plus factors like more elevation changes, extra use of the AC due to humidity, etc.

That being said I only ever got 28mpg or so on my long highway trips. Granted that was 75mph+ with the top down and use of the on ramps like they were runways

Glad to hear that people can crack 30+ mpg if they really try.

Kyras

I'm talking about my mileage on the whole trip, including before I put the new tires on in Cranberry Township. I'm also comparing it to trips Jerry and I made, and many others in the same terrain. The air cleaner and spark plug data are in the book I didn't bring, so I'm not sure when they were changed last. I really thought I was up to date on everything before planning this road trip.

Kyras

Okay, I thought about it and looked, and I did have my first Auto Record "At-A-Glance" book in my S. Plugs were changed at 58,007, so 30,000 miles ago. Air cleaner was changed at 50,902 so 38,000 miles ago, and that was 3 years ago. Am I a bad girl?

I now have just my old book with me. I'm not 100% sure I haven't changed the air filter since then, but it could be. I'll go back to the car and look again in a few.

Morris

Patty, I think the further east you go the more humid and thicker the air gets, meaning more wind resistance. That's the reason, I'm sure.