4th Gear RPM w/auto?

I have an 88 LXI with a automatic transmission and FI 2.0. Just wondering what the RPM should be at when crusing at 55mph. The 3rd tank I've had through the car has yielded 22mpg on the freeway and the car is running at 2400-2500 RPM. To me this seems too high but I don't know for sure. The previous owner told me it would get about 36mpg on the freeway. The oil, tranny fluid, fuel filter, and air filter are all new and I ran Lucas upper cylinder lubricant the 1st two tanks. I also put 205-40-17 tires and magnesium wheels that weigh the same as the factory wheels. Thanks for any help!!

How are the spark plugs and wires? 22mpg is way to low. As for the RPM's, not sure.

try a 4 wheel alignment, take to a good place with pc based system on the rack.

I have not changed the plugs or wires yet but the wires test good, have not looked at the plugs yet. Which wires and plus do you recommend, does NGK make wires for the car? Would the 1/2" taller tires hurt or help the mileage. I would think they would help because every revolution you are traveling further but do the add strain to the engine this size?

I was going the get the alignment checked this weekend. The car goes down the road perfect right now. It doesn't pull either way, the steering wheel is straight and it travels down the road very smooth. Can mis alingment take more than 5mpg away?

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Originally Posted by oline897

I have not changed the plugs or wires yet but the wires test good, have not looked at the plugs yet. Which wires and plus do you recommend, does NGK make wires for the car? Would the 1/2" taller tires hurt or help the mileage. I would think they would help because every revolution you are traveling further but do the add strain to the engine this size?

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NGK does make them i believe. I use Duralast from Autozone with the lifetime warranty.

At 55 mph with my auto tranny i'm usually closer to 2000 RPM. I get in the 2400-2500 range at near 65 mph. Then about 2900 at 70 mph.

That sounds more like the right RPM something must be wrong. I know it is in 4th gear, anyone have any ideas?

The basic Bosch platinum plugs (not +2 or +4) are awesome! Your mileage is really bad. Even with my #4 cylinder burned up, I still got 27 mpg. How does the car run otherwise? Is poor mileage your only issue?

The car runs perfect. Idles smooth right at 800rpm and no hesitation any where. I think the car is running at too high rpm when at 55mph in 4th gear. Like mentioned above the car should run around 2000rpm instead of 2500 rpm. This could kill my mileage. I just have know clue where to start looking for a problem.

could be your overdrive is not working....do a tranny flush and fill it up with new fluid

My '93 Accord's torque converter never locked up consistently. It drove me bananas. I took it to shops but they always said it was working just fine. When the Bridgestone tires on it wore out, I bought Michelins and it's worked flawlessly ever since. Go figure.

Maybe you should check your cap and rotor as well.

Another biggie for me when my mileage was at 18-20 (still ran fine somehow....?) was i replaced both O2 sensors. Made a huge difference. i shot immediately up to 26 mpg, and the next week i replaced the cap and rotor, and shot me up again to 30.

The trans fluid is new. I will try replacing the plugs, wires, rotor, and cap next and see what happens. Does it make a difference if the trans is flushed completely. I just drained and refilled around 4 qts. In the manual it say if your doing a complete rebuild it takes more fluid so there is still some old fluid in it. The fluid is Mobil 1 synthetic Dex III if this could have anything to do with it. Again thanks for the help!

i would only use honda ATF fluid on these trans.

I'll try changing to Honda ATF and see what happens.