Porsche 1976 911s MPG

[Derrick11]

Hey Guys,

New to this forum, and have a quick question that I can't stop thinking about. Today I bought my first Porsche, a g-series 1976 911s with the stock 2.7 fuel injected engine. I bought the car In Tucson, AZ and drove the car back to Los Angeles. I filled up as soon as I got the car, and hit the road directly after. It took me about 8 hours and was 523.5 miles to be exact. These cars have a 21.1 gallon tank, and once I arrived home, I had just over a half a tank of gas left. I did NOT stop once to fill up, I repeat I made it all on a half a tank. Doing the math, I averaged 49.9 mpg.(21.1 divided by 2= about 10.5 since I had a half of tank left, and then divide that by 523.5). How the hell is this even possible?! And yes all of the gauges are accurate to the tee, I also was using my phone to verify mpg results the entire time. Just to throw this in there I was going 60mph the entire drive in 5th at just under 3grand.(Didn't want to push the car my first trip ) What am i missing? Can this 40 year old car get almost better mpg then a 2016 Prius? Thanks.

(I also read in previous forums that most average around 25-30 mpg highway in the same car)

[grant lyon]

It looks as though you are using the fuel gauge, not a refill of the tank, to determine the fuel consumed over a distance traveled; the gauge is hardly accurate enough for this purpose. The gauge is not linear (look at the markings), the float can stick, etc. etc. Assuming 25 mpg, you may be about to run out of gas. Suggest you refuel (fully) to get an independent (gas pump reading) verification of fuel use and to avoid being stuck on the side of the road.

[timmy2]

My gauge used to stop 1/2 way. Almost ran out of fuel!
I don't trust it even after replacing the sender that was stuck.
Measuring how many gallons to fill up the tank again is the only true way to check mileage.

[Derrick11]

Hey Grant and Tim thanks for the reply, I originally thought the fuel gauge was inaccurate as well until I filled up shortly after I got home and it cost me $17 bucks to top off. Maybe its just Shells "Superior gas" lol. Any other possibilities or explanations you guys can think of because I'm baffled.

[Jrboulder]

How you drive has a big impact on mpg. It sounds like you drove in a highly efficient way. Years ago my friend and I drove his Ford Ranger to pick up some Porsche parts 150 miles each way. We started with a full tank and he drove 80 mph the whole way down with the gauge indicating 1/4 tank when we picked up the parts. I drove back at 60mph on less than the remaining quarter.

[rwest]

I once got 39 mpg on an older 911, it had very low compression because of bad rings, I figured that was the reason. My 77 gets 26 or 27 on highway road trips. Maybe you have a steep 5th gear as well? What are your RPMs at cruising speed?

Very curious for sure.

[billh1963]

I have a 76 with a newly rebuilt 2.7. I see numbers close to 30 on a regular basis.

Unrelated: Out of curiosity, what oil pressure were you seeing in 5th gear at 60 mph?

[pete3799]

Originally Posted by Derrick11

Hey Grant and Tim thanks for the reply, I originally thought the fuel gauge was inaccurate as well until I filled up shortly after I got home and it cost me $17 bucks to top off. Maybe its just Shells "Superior gas" lol. Any other possibilities or explanations you guys can think of because I'm baffled.

How many gallons is $17 bucks in LA?
According to Microsoft Streets & Trips Tucson to LA is 486 miles.

[boyt911sc]

Originally Posted by Derrick11

Hey Grant and Tim thanks for the reply, I originally thought the fuel gauge was inaccurate as well until I filled up shortly after I got home and it cost me $17 bucks to top off. Maybe its just Shells "Superior gas" lol. Any other possibilities or explanations you guys can think of because I'm baffled.

Derrick,

Either you are lying or have a poor memory. There is no way in the world you could have gotten this mileage. Period. Even if you drove at a very slow pace. I will pay for a full tank if you drive again a 500 miles trip (without refilling) and with reliable witness. Maybe in your excitement you have forgotten that you stopped once and got your tank filled up. There must be a reason for this to happen and you are not telling us everything.

BTW, G-Series production is from August '73 to July '74 for 911 cars. And the fact that it took you $17 to refill your used 10 gallons is weird. Congratulations. You just found the Holy Grail of automotive engineering.

Tony

[bbturbo]

Shell's V-Power is great gas... if that is what you are actually getting. Sometimes I fill up and my fuel economy is tragic and sometimes its amazing... I got 27mph on a tank and then the next was 22... same exact type of highway driving, same conditions, etc. I do not trust the gas stations, especially when I have known of BP owners selling reg at prem. price in Indianapolis.

There are a lot of variables that go into play to get spikes in fuel economy and downs.

[al lkosmal]

put down the pipe...........


regards,
al

[74-911]

Originally Posted by derrick11

hey guys, .......how the hell is this even possible? it's not

......... Can this 40 year old car get almost better mpg then a 2016 prius? Thanks. NO

I can push 30 if I drive very conservatively on the highway... but the highway speed limits here are 75 and just driving the speed limit can get you run over in most places...
I am usually in the low 20's if that ...

after all, the power band starts around 4K RPM

[75 911s]

I installed Hydraulics on my 75. At freeway speeds I lift one wheel off the ground to reduce drag. I also unplug two spark plugs for less fuel consumption. I've gotten over nine thousand miles per 500 gallons. You do the math.

All kidding aside welcome! 25mpg seems like a reasonable number. Remember. All roads lead back to Tucson.

[Algernon]

Maybe the gauge is off and you are nearly out of gas. Even so, as you did not actually run out of gas, that's pretty good going. So 523 miles using about 20gals comes out to a more realistic 26mpg. Don't think you are lying or have poor memory, just a nice car and careful driving. See how many gals it takes to refill it, and let us know. Well done!

[boyt911sc]

Originally Posted by Algernon

Maybe the gauge is off and you are nearly out of gas. Even so, as you did not actually run out of gas, that's pretty good going. So 523 miles using about 20gals comes out to a more realistic 26mpg. Don't think you are lying or have poor memory, just a nice car and careful driving. See how many gals it takes to refill it, and let us know. Well done!

Algernon,

Derrick spent $17 to refill his gas tank after driving 523 miles!!!!!! You got to be 'something' to believe such information. Unless you are gullible. Remember this is a technical forum and discussions based on facts not myth.

Tony

[Derrick11]

Problem solved; gauge is off, and yes I paid 17 bucks last night to "top off" because gauge showed that It was full. Went back to gas station this morning ended up putting another half a tank in. However did still drive 500+ on one tank.

P.S.boyt911sc (Tony) The negative comments are awesome, thank you. I forgot how welcoming these forums were. Im happy you think I take the time out of my day to get on here and lie about some mpg bull****, or forget that i filled up lmao. Your great, Such a big help, and seem quite intelligent! Im sure you add an abundance of help to these forums and everybody loves you. Im also pretty sure, it makes you feel good. Being that you got on this morning at 6:31am to troll on this thread, and got right back on at 11am to troll some more. Hell you were probably on these forums the entire time. Anyways thanks again big man, keep it up!

[boyt911sc]

Originally Posted by Derrick11

Problem solved; gauge is off, and yes I paid 17 bucks last night to "top off" because gauge showed that It was full. Went back to gas station this morning ended up putting another half a tank in. However did still drive 500+ on one tank.

P.S.boyt911sc (Tony) The negative comments are awesome, thank you. I forgot how welcoming these forums were. Im happy you think I take the time out of my day to get on here and lie about some mpg bull****, or forget that i filled up lmao. Your great, Such a big help, and seem quite intelligent! Im sure you add an abundance of help to these forums and everybody loves you. Keep it up.

Derrick,

Like I said before, this is a technical forum. When you came and declared that you drove 500 miles and cost you $17 fuel is absurd. If you have any common sense in your head, you would think twice before posting this information. You might get away in some other technical forum in the Internet, but not here in PP. Most readers in this community are smart and not gullible. Do your homework before you cry wolf. We all make stupid mistake including myself. And learn from this mistake.

Tony

[RSTarga]

Have you ever heard of Ballonfoot Bodine?

[Derrick11]

Tony,

Back here trolling again huh?! I came to this thread because my results DID seem absurd, if you would have read my initial post. Simply wanted others results taking into consideration (non-faulty parts). Thanks again though for the negativity. And yes we all do make mistakes, I just hope you never make the mistake of talking to people this way anywhere other then your favorite "PP" forum, behind your computer screen. Im sure you don't though, you seem to have much more "common sense" then I do. Really this time, thanks for your help.

Derrick

[rwest]

Originally Posted by Derrick11

Tony,

Back here trolling again huh?! I came to this thread because my results DID seem absurd, if you would have read my initial post. Simply wanted others results taking into consideration (non-faulty parts). Thanks again though for the negativity. And yes we all do make mistakes, I just hope you never make the mistake of talking to people this way anywhere other then your favorite "PP" forum, behind your computer screen. Im sure you don't though, you seem to have much more common sense then I do. Really this time, thanks for your help.

Derrick

Derrick,

Tony is a straight shooter and maybe that came off as being rude to you, he was just trying to help you get to the root of your rather incredible gas mileage problem in a quick fashion. Tony is one of the top couple guys when it comes to trouble shooting the CIS fuel injection systems on our cars, he has gone above and beyond for many of us and I'm sure he would step right up and help you trouble shoot yours too if the need arises.

May I kindly suggest that you give him the benefit of the doubt and let this go?

Welcome aboard and I think you'll find that this forum is very much unlike the others you may have encountered- lots of good people giving good advice, very little bickering, well unless you go to the PARF section of the forum!

It is also customary to post a picture of your car here when you join up.

Best,
Rutager