81SC - 10 MPG?!

Does anyone know what kinda of mileage I should be getting? I'm drive my car to work everyday since I bought it 5 months ago and the gas bills are starting to add up. The car has had a recent tune-up with new points, timing, valves, etc.

Anyone thoughts on improving mileage, I'm think about checking...
1. Make sure AC is not engaged full time
2. Another tune-up
3. New wheel bearings

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81'SC Targa

If your shop charged you for new points, you may want to find a new shop.

How old is your O2 sensor?

What kind of driving do you do? If you do all city, lots of stop and go, an SC can get pretty low mileage, although 10 mpg sounds a bit too low. I'd hook it up to an exhaust gas analyzer to make sure that it is running at the right mixture. With a properly operating Lambda system, you should be doing a bit better on the mileage, is my guess.

Dragging an anchor from a heavy cruiser? Brakes? Coldstart valve? Check that puppy out cause raw gas is going to destroy your engine! Or do you live on Hudson's Bay and drive less than a mile each way to work? In which case your probably doing okay, but the raw gas will kill your engine!

Thanks for the tips. I'll try and get the mixture analyzed, it seems pretty rich when it starts cold, but gets better.

I do drive frairly agreesively when I'm not stuck in stop an go traffic. However it seems to get worse mileage if I'm going 75 then if I'm going 5 mph.

Diverdan,
What do you mean by "raw gas"?

Are you refering to the cold start valve?
What kind of harm are you talking about?

Leland:

Raw gas is unburned gasoline in the combustion chamber. It has a nasty tndency to wash away the lubricating oil in the cylinders, pistons, and rings. In extreme cases it may contaminate your oil in the sump. If you sniff the dipstick in such a vehicle you may be able to detect the smell of gasoline. The result is premature wear. You've probably seen this on some old vehicle you had in Michigan that had a stuck choke.

I too have an 81SC, UK model and consistently get around 20 mpg, better on the opem road and worse around town.

So you would appear to have a problem!!

Neil
81SC Targa

Hell, even on my old MFI car with my foot usually firmly planted on the right pedal I never get worse than 13-15 on the street...usually more like 17-19...a CIS car should get closer to 20 if not more.

My '78 SC gets about 15mpg. I spend 50% of the time on the freeway, 40% rural roads ands 10% town. I recently fixed a fuel leak that was causing me to get 12mpg, baaaaad leak.

I drive my 81 SC Targa mostly in town. I always intend to keep my foot out of it at least for one full tank of gas but never do. I get about 17 mpg.

If your bad fuel mileage is caused by a rich condition (vs a leak or VERY aggressive driving) then your oil is being contaminated as well and should be changed as soon as this problem is fixed, if not before. Cheap insurance. My '78SC w/CIS gets 25mpg combined driving. I don't have A/C or any power options, but I do drive hard wenever the roads are clear of those pesky commuters.

I was getting 14 around town , before a tune then 10 afterward. My shop had adjusted my alignment with 190 lbs in the left seat,huh? When I asked them to return it to factory specs I got back to 14 . On the open road I never get less than 25 , more like 27-28. The original mileage estimates when our SCs were new was combined 18 I believe! I would be really curious to see what would happen if I just poked along but that just ain't happening! Check your tune , o2 sensor and alignment, something isnt right.

I knew there was a reason I needed to repair my odometer!

I got 24 once. At 85 to 90 mph. No kidding. Better mileage than the lower speeds. I usually get 18 to 21.

Oh, and if any WA State Patrol officers are here, it shoudl be noted that these tests were conducted in controlled conditions. I would never exceed the speed limit on public roads.

My best advice is to check the tune-up. Exhaust analyzer is good. Ignition system. Either it's getting too much gas, or its not lighting all the gas its getting.

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'83 SC



[This message has been edited by Superman (edited 11-22-2000).]

I have that same test area here in Louisiana. Surely they must set aside these areas just for us. I think there is something in the VIN that makes a Porsche exempt from speeding tickets within the confines of these special sections of road. Please correct me if I'm wrong.

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Robert Stoll
83 SC
83 944

Learned my lesson. Again. When I fill with gas I push the trip odo button and write the mileage on the receipt. I don't usually do anything with it, but I started to become disappointed with my mileage and at a glance the numbers. Checked my Beru connectors, knowing one was poor. Three were bad. Explains my rough startups too.

With new Berus there is greater smoothness and I'll wager, restored economy. FWIW.

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'83 SC

You know, 30+ years ago ... the racers and hi-perf paranoid 'types' used to swear at anything but non-resistor plug connectors, and solid-core wires! I always wondered why, and couldn't believe it was power, or anything related to tuning, but if memory serves me right ... that was what they always claimed! I am beginning to thing they were right about the connectors ... but WRONG about the reasons for doing it! I have seen far more 'bad' connectors on VW type 1, 2, and 3 engines than for 911's, and it doesn't matter much about having to change out a set of sparkplug wires when it is less than $10! But, as you all know ... replacement wires for 911's are astronomical, and I have always hesitated to replace something that can be salvaged or rebuilt with reliability and cost-savings combined. So, I always encouraged people to replace old, aging neoprene wiring with silicone wire. And I always mention the possibility of Beru connectors gone bad, but I suspect there are those that think checking sparkplug wires for resistance is a waste of time!

Considering the number of people I have heard about finding bad Beru connectors, I wonder if they shouldn't be checked at every change of sparkplugs! And, old wire sets should NOT be thrown away! At the minimum, keep the old distributor and sparkplug connectors!!! I really think there is a lesson in Superman's experience!

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Warren Hall
1973 911S Targa