Very low mpg, help plz

[particlewave]

3.2k is really low. Keep your shifts between 4k-5k+. At about 5.5k, that engine really sings.
Even with that said, you should be getting better mileage.
My 2.5 gets roughly 20 city, 25+ highway, even on 91 octane.

[Mike689]

I guess I'll use some injector cleaner, fill up the tank with chevron a couple of times, and replace the spark plugs. I hope this takes care of it.

[Mike689]

Originally Posted by particlewave

3.2k is really low. Keep your shifts between 4k-5k+. At about 5.5k, that engine really sings.
Even with that said, you should be getting better mileage.
My 2.5 gets roughly 20 city, 25+ highway, even on 91 octane.

On 6th gear going 65mph the RPM is around 2.5k. Should I be using 5th gear then?

[Fintro11]

how is your air filter / tire pressure?

[911monty]

Originally Posted by Mike689

On 6th gear going 65mph the RPM is around 2.5k. Should I be using 5th gear then?

Yes; Listen to your engine and feel the pressure you are using on the throttle. The engine will communicate back to where it wants to run. You will have much better results. I have driven my 2.5 into So CAL down the 215 rarely using 5th gear and have gotten 32 calculated freeway. I believe you are so low in RPM the knock sensor is retarding the ignition timing. Try keeping at 3.2k +. I don't think your plugs are an issue since you just bought car so had to pass CA smog. Of course new plugs are always good.

PS; I used to have an air cooled 911 with weber carbs hat would load up below 3.5k. This was during the famous 55mph speed limit days. I used to have to shift constantly between 2nd and 3rd that car really hated that speed limit. Now at 90 Yahoo!

[BIGJake111]

Originally Posted by BYprodriver

In CA!, that's more illegal than pot!

So that's why they all drive teslas when they want to go fast!

I honestly did not know that such a socialist thing could happen in the land of the free . (I kid, however I do enjoy my right to 93 octane, no front plate, and no emissions test, then I regret that right when a truck carrying a confederate flag "rolls coal" across the intersection.)

[Mike689]

Originally Posted by Fintro11

how is your air filter / tire pressure?

The tire pressure is fine I checked it 2 days ago. I should probably change the filters though.

Originally Posted by 911monty

Yes; Listen to your engine and feel the pressure you are using on the throttle. The engine will communicate back to where it wants to run. You will have much better results. I have driven my 2.5 into So CAL down the 215 rarely using 5th gear and have gotten 32 calculated freeway. I believe you are so low in RPM the knock sensor is retarding the ignition timing. Try keeping at 3.2k +. I don't think your plugs are an issue since you just bought car so had to pass CA smog. Of course new plugs are always good.

Damn I'm such a newbie lol. I've driven a manual car before but it wasn't a sports car and this my first car with manual. So I've been lugging my engine for like 3 weeks I hope I didn't screw things up too bad.

[Mike689]

Originally Posted by BIGJake111

So that's why they all drive teslas when they want to go fast!

I honestly did not know that such a socialist thing could happen in the land of the free . (I kid, however I do enjoy my right to 93 octane, no front plate, and no emissions test, then I regret that right when a truck carrying a confederate flag "rolls coal" across the intersection.)

LMAO! I thought u were being serious for a second there.

[911monty]

Damn I'm such a newbie lol. I've driven a manual car before but it wasn't a sports car and this my first car with manual. So I've been lugging my engine for like 3 weeks I hope I didn't screw things up too bad.[/QUOTE]

Mike; I went and looked at your original posts and hopefully without starting a war I noticed you are aware of the IMS. There is lots of informative reading on this subject in here when you have time and popcorn. Jake Raby is a very knowledgeable resource. I hope he doesn't mind my referencing him but he has stated that the IMS has the most loading at low RPM. IMHO This is why there is a theory that engines that have been driven hard have less IMS failure than a garage queen, Lugged around engine. Hence the statement Drive it like you stole it! These cars love to rev! Their pedigree is racing. Get out and enjoy the way it was meant to be driven!

[Mike689]

Thanks. I hope to get the IMS and clutch replaced as soon as I have the money. I had a mechanic tell me a LN and the pelican parts bearing both failed on him. I don't think I believe him lol.

[911monty]

Mike there is something else that is bothering me about your thread. You say you have filled up once in 3 weeks and getting 16 mpg. That only works to a maximum of around 240 miles a week or around 10 miles a day. Are you only driving around 5 miles one way? Sorry I'm not trying to pry, but, short trips are also bad.

[epapp]

It couldn't hurt to disconnect the battery, turn the key in the ignition to drain all power, and then reconnect the battery to reset the car's learned driving/throttle values. That, combined with your new gas type, injector cleaner, trying a different gear on the freeway etc will rule out all of the easy things.

[hancock1701]

Originally Posted by 911monty

Mike there is something else that is bothering me about your thread. You say you have filled up once in 3 weeks and getting 16 mpg. That only works to a maximum of around 240 miles a week or around 10 miles a day. Are you only driving around 5 miles one way? Sorry I'm not trying to pry, but, short trips are also bad.

Sorry I don't mean to hijack OP's thread, but since this is here, I need to ask. I know short trips are bad, but from my understanding, it's because the engine hasn't had time to warm up properly, so basically short trips are cold driving trips. I currently do 5 miles one way too, no freeway, takes a bout 12 minutes. But the engine temp always get to 180 on the gauge when I get there, so I assume my engine is safe?

[911monty]

Originally Posted by hancock1701

Sorry I don't mean to hijack OP's thread, but since this is here, I need to ask. I know short trips are bad, but from my understanding, it's because the engine hasn't had time to warm up properly, so basically short trips are cold driving trips. I currently do 5 miles one way too, no freeway, takes a bout 12 minutes. But the engine temp always get to 180 on the gauge when I get there, so I assume my engine is safe?

Hancock; You are correct. Now I don't wish to pass off my idiosyncrasies I've developed from my years of driving an shall we just say array of vehicles. This was crucial in older carbureted cars where chokes caused raw fuel etc in the oil pan. Current fuel injection has gone a long way to deal with the cold start issues. However the logic still continues that lots of freeway miles are much better than many short trips. Reason is systems haven't stabilized at "Normal" temps to cook off the contaminates that have condensed into oils, trans included, forming corrosive contaminates in the engine etc. 5 minute trips hardly recharge the battery from the start! Many opinions, mine included, but I try to drive no less than 20 min after normal temp achieved. SO get out there and paste a grin on your face a little longer! Oh the horrors! LOL.

[JayG]

Interesting comments about shift points

If I am doing just regular cruising, I shift right around 3k. For performance, I'm looking around 5.5-6.5k shifts. On the track, I may hit the rev limiter every now and then. On the freeway in 6th, 3k =~78 displayed, 75 actual mph, right at the bottom of the power curve.

[Mike689]

Originally Posted by 911monty

Hancock; You are correct. Now I don't wish to pass off my idiosyncrasies I've developed from my years of driving an shall we just say array of vehicles. This was crucial in older carbureted cars where chokes caused raw fuel etc in the oil pan. Current fuel injection has gone a long way to deal with the cold start issues. However the logic still continues that lots of freeway miles are much better than many short trips. Reason is systems haven't stabilized at "Normal" temps to cook off the contaminates that have condensed into oils, trans included, forming corrosive contaminates in the engine etc. 5 minute trips hardly recharge the battery from the start! Many opinions, mine included, but I try to drive no less than 20 min after normal temp achieved. SO get out there and paste a grin on your face a little longer! Oh the horrors! LOL.

According to the manual you aren't supposed to warm up ur car idle. It says to drive the car immediately after start and don't go over like 4.5k rpm for first 5 minutes.

[Mike689]

Originally Posted by JayG

Interesting comments about shift points

If I am doing just regular cruising, I shift right around 3k. For performance, I'm looking around 5.5-6.5k shifts. On the track, I may hit the rev limiter every now and then. On the freeway in 6th, 3k =~78 displayed, 75 actual mph, right at the bottom of the power curve.

That's how I've been driving, I'm a little confused. Do you have the base model or an S? Wouldn't the rpm and shifting change?

[911monty]

Hey JayG; Good to have an instructor chime in! I hope I'm not giving bad info. Some of my style may be due to my driving a 2.5 so keeping it in the power band (3.2k+) is a job. When on the freeway I typically don't use 5th until above 75 indicated where I can keep in the aforementioned power band. That said in response to the OPs question regarding poor fuel mileage my thought is he is shifting just as he is entering the power band but more importantly may be spending too much time below the power band and in the lugging range of the engine with the knock sensor picking up the gears/chains lashing, then retarding ignition timing causing the poor fuel economy? If he is shifting 3.2 k then he is 2.2k after shift. OP lives in Monterey so as I'm sure you know it is not all sea level driving there. Viva Laguna Seca!:dance:

[JayG]

Originally Posted by Mike689

That's how I've been driving, I'm a little confused. Do you have the base model or an S? Wouldn't the rpm and shifting change?

I have a S with a 6 speed, so yes, the shift points could be a little different as to speed. In any case I don't see why you need to rev high for just cruising other that the wonderful sound at higher rpm. Certainly don't want to lug the engine either.

IIRC many that track the 986 prefer the 5 speed because of the gear ratios

[JayG]

Originally Posted by 911monty

Hey JayG; Good to have an instructor chime in! I hope I'm not giving bad info. Some of my style may be due to my driving a 2.5 so keeping it in the power band (3.2k+) is a job. When on the freeway I typically don't use 5th until above 75 indicated where I can keep in the aforementioned power band. That said in response to the OPs question regarding poor fuel mileage my thought is he is shifting just as he is entering the power band but more importantly may be spending too much time below the power band and in the lugging range of the engine with the knock sensor picking up the gears/chains lashing, then retarding ignition timing causing the poor fuel economy? If he is shifting 3.2 k then he is 2.2k after shift. OP lives in Monterey so as I'm sure you know it is not all sea level driving there. Viva Laguna Seca!:dance:

Not an instructor (yet, maybe one day) but an enthusiast.

I don't see how shifting below 3.5 will reduce MPG. If anything running at higher RPM will decrease MPG. My 996 has a tip ( same tranny as 986 tip) and unless I am putting my foot into it, will shift right around 3k My guess is the tip in a Boxster will shift pretty much the same.

I would think that higher RPM = lower MPG n matter what gear or tranny you are using