There's nothing wrong with 5th @40mph. I'm often in 6th by then for fuel economy reasons. This whole discussion is predicated on a mileage prediction based on faulty input data. Wait for the OP to do an actual mpg computation using real mileage and real fuel consumption, then we can speculate about hardware problems

 

I've been driving for 45 years - not all of them in standards - but in normal driving, city or highway, I have always believed that the proper thing is to shift at or just under 3K on the tach. I have never had any consciousness of relating gear selection to road speed. Never.

If you follow that rule of thumb you never have to question if you are doing it properly and you will achieve the best combination of performance and efficiency.

If you are on a sport bike, however, just add 2.5K to the formula!

 

I would actually say that running in too high a gear for the road speed is counter productive as far a economy is concerned, as at those sort of speeds the engine is actually laboring, rather than running freely, even an auto-box will not sit in 5th @40mph.

As for the OP fuel consumption, in order to achieve those sorts of figures, i would have to be on a track holding red-line in every gear to get close, so unless he really cant drive or calculate, then theres a problem.

 

change your air filter

 

You can hear when the engine is lugging. 6th@35mph is about the slowest you can go before it starts lugging, and only if it's just cruising on flat ground. The auto has different gear ratios that's why it won't stay in 5th.

I have been on track holding full throttle in the 5k RPM to redline range and tracked my mileage, and I got around 7mpg, but this really is wide open throttle most of the time and not something you could come even remotely close to on the street. If I drive in a spirited fashion around town, 15mpg is about reasonable, more conservatively I straddle 19mpg, and highway cruising is about 26-27mpg. (I'm on of those **** types who tracks gas mileage in a spreadsheet).

 

I presume there is nothing else obviously wrong, like black smoke / sooty exhaust or low engine temp? I've seen poor mileage on other cars from either bad O2 sensors or a bad thermostat. The latter can cause excess fuel consumption because the engine is always in "warm-up" mode and using richer mix and higher RPMs.

 

I'll sometimes be in 6th at 40-45 if the road is flat and be around 1200-1300rpm

 

Definitely gotta try this 35mph in 6th gear thing. I usually stay in 5th gear in the city going 35-50. Never went to 6th lol.

 

Usually if I'm on flat I try and keep RPMs near 1200, if not perfect flat 1500 and hills 2000 and up

 

Motors are like speakers. Too low RPMs or power cause problems. Speakers clip when not enough power to complete an excursion, and engines are actually made to run at high RPMs.

Since these cars lack torque, running a manual at or just over 2k RPM is a good city level. In Supercharged cars, where torque can MAX at 2400RPMS, you can run into the teens.

As above, regular casual driving shouldn't involve any RPM higher than 3k.

If you shift prior to 3k, driving in the 2k to 2500 RPM range at cruise, and don't floor it at 35mph in 6th (driving in 6th at 35 is an assinine design)... you have a mechanical issue.

Follow the advice given, recalc on a few full tanks while driving causally. Then look into mechanical cleaning or diagnostics.

These cars desperately need an overdrive gear, both in manual and auto configs. 3k+ RPM at 80mph in an auto for a $35k car (new) is stupid.

 

Personally I own a 5at, but I used to have a manual in another car which was a 6spd. You should definitely at least be in 5th gear around 45-55. Also throwing your car into neutral isn't going to save you gas because the engine is using fuel to keep it idling where as if you keep it in gear, I'm not sure what it's called, but it cuts off fuel and uses purely your moving speed to keep the engine going.

If you need power to pass or something, that's why you downshift...

 

WoW you all drive so different to us across the pond. Putting the car in nuetral to coast up to lights you know you have no real control in nuetral if something were to happen, gears should be engaged at all times so you always have control of the car. Next you will be saying you coast around corners
Anyhow isn't coasting illegal in the U.S ?

As for 5th gear at 40mph this will put strain on the motor as though you were towing a trailor. This can be worse for the engine than high reving it.

Maybe its because you all have an auto transmission history of driving where we are tought to drive manuals before moving onto autos at around mid age but probably mostly due to the nature of our roads having more corners and tight bends in etc.

BTW what wories do you all have when your fuel is so cheap, try paying
$7 or $8 a gallon like us along with $600 a year road tax

 

Only engine braking in certain citie limits and for truckers. I dont like doing it so i just use it to stop at the light instead of using my brakes as much.

 

Just filled up, 10.5 gallons for 98 miles, so about 9.3 mpg. That was before I started shifting at 2k, so I've been trying that for a few gallons I'll get back to you guys in a few days once I fill up again.

 

Huh. I had no idea neutral used more gas than in gear. I suppose I'll work on that too from now on.

Another question no one really answered, is gas use related to rpm's or to the amount you depress the pedal?