Advice on gasoline / additives

[Crazy Horse]

With the risk of being the newbie that posts too much...

In an earlier post I said that I am using 100LL AvGas in my 79 3.0 and I swear I can tell the difference (may be a delusion of Porsche addiction).

I am planning for a long trip on public highways and wondered if anyone had any thoughts about what cocktail can be effective with pump gas? Which brand of gas best to start with?

Also:

1.) How to keep a marriage while in love with a Porsche 911
2.) Excuses for driving when all of the obvious ones are used up
3.) Explaining why the arrival of a box from Pelican Parts means we will not be seeing a movie this weekend

[Danny_Ocean]

Originally Posted by Crazy Horse

1.) How to keep a marriage while in love with a Porsche 911

ChemTool B12 (do a search...additives discussed in depth very recently).

Stay single (also discussed recently).

[rusnak]

haha I love this thread already.

My current gf is having trouble with my "ground rules" that the dog and the air cooled 911 are non-negotiable items....I come with baggage, in other words. I read somewhere that these are cars that inspire us to sacrifice for them. No truer words were ever spoken.

Anyway I don't think any exotic gas blends are necessary or even good. I swear by using the highest octane gas you can find, and about every year or less buy a can of BG 44K and add it to a full tank. You will feel the difference. I don't usually buy Chevron or add Techron unless I'm getting lazy and want to clean my injectors the lazy man way. BG makes a fuel injector cleaner that is weaker than 44K, but I can't remember what it's called. I don't buy it because it's not as potent, and I think it's sort of a waste of money.

I use the excuses that (1) owning a car that you can work on versus take to the shop saves money, (2) selling the 911 won't yield enough money to result in actual savings, but rather the opposite, (3) car ownership is a long term proposition, not about sniveling every time stuff breaks down, (4) working on the car is my therapy, saves us money, and is cheaper than fancy Dr. supervised therapy.

[911s55]

Why do you need an additive?

A stock 3.0 with an 8.5 compression ratio should run great on Chevron (already has Techron additive) 89 octane and even 87 in the winter.

I also run Shell, there are many other top tier gasolines.

[morrisjm1]

Jack,
Here's what I remember about avgas in cars from college when I was getting my A&P:

1) Unless you're running a high compression engine, the extra lead can do more harm than good. If the combustion temps aren't high enough, the lead can precipitate out in the exhaust stream and damage the valve stems over time.

2) 100LL has less lead than the old 100/130, hence the name "Low Lead", but has twice the lead of the old 80/87. That's a lot of lead for an engine designed to run on unleaded gas.

Of course, that was about 30 years ago, so I might not be 100% correct, but I still think you'd be better off not burning avgas if your engine is stock.

Enjoy your trip.

Mike

[Crazy Horse]

The little door that you have to open to put gas in the car has a sticker that reads "AVGAS Only GRADE 100LL GRADE 100".

Why does it say that? - it looks factory to me. See pic below:

[PatrickB]

Originally Posted by Crazy Horse

The little door that you have to open to put gas in the car has a sticker that reads "AVGAS Only GRADE 100LL GRADE 100".

Why does it say that? - it looks factory to me. See pic below:

Nah... It would be in German!
Someone is playing a big joke on you!

Running AV gas in your stock SC is a complete an unnecessary waste of $$$

[tcar]

Yep, even 93 octane (91 here, a mile high) is a waste.

[Crazy Horse]

I want to be sure about this. I've ran against a couple of other SC's and my car clearly pulls harder and winds higher through the gears - but you could be right.

I want to know for sure...any other out there with wise expertise on this decal?

It fits too good in the door inside and looks authentic - somehow. It's been on the door for a very long time (you'd have to see it in person). No attention was drawn to it by the previous owner during "sales" talk.

Any assistance would be greatly appreciated.

BTW: Only 8.5 compression? I need to put that on my "long-term" project list.

[Danny_Ocean]

Originally Posted by Crazy Horse

I want to know for sure...any other out there with wise expertise on this decal?

It fits too good in the door inside and looks authentic - somehow. It's been on the door for a very long time (you'd have to see it in person). No attention was drawn to it by the previous owner during "sales" talk.

Any assistance would be greatly appreciated.

Readily available on E-Bay. Made for small planes:

http://cgi.ebay.com/ebaymotors/Avgas-only-wing-decals-2_W0QQitemZ4643563067QQihZ017QQcategoryZ26440QQssP ageNameZWDVWQQrdZ1QQcmdZViewItem

And here's the "Jet Fuel Only" upgrade:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=4643563694&ssPageName=MERC_VI_RSCC_Pr4_PcY_BIN_Stores_IT&refitem=4643563067&itemcount=4&refwidgetloc=active_view_item&usedrule1=StoreCatToStoreCat&usedrule2=CrossSell_LogicX&refwidgettype=cross_promot_widget


So now...tell us about the "wing flaps" mod again...?

[morrisjm1]

There has never been a car that requires avgas. The litte dot at the end of the last sentance is a period. It just doesn't make any sense.

There are lot of urban legends about, "How fast my car went on avgas", but there just isn't any truth to them. Avgas and car gas have about the same BTUs/lbs, the difference is that avgas has a higher vapor pressure and a higher octane rating than car gas. The higher vapor pressure is to reduce the possibility of vapor look at altitude in airplanes that don't have in-tank fuel boost pumps and the higher octane rating is to reduce the chance of detenation. Airplane engines are have relatively high displacements for their horsepower ratings, as a safety measure. Therefore, they typically have big bores, fairly long strokes, high compression and turn at low RPM, by car standards. They have dual ignition to reduce the chance of detenation, as well as a safety measure.

If you have a stock SC, avgas, as mentioned by other posters, is a complete waste of money, may damage your engine and is damaging the environment. Save your $$ and buy some SSIs, that's what I'm saving for.

Mike

[4flyboy]

That sticker on the inside of your gas flap is standard fare on just about any light aircraft............
somebody is having fun.

S.

[Crazy Horse]

You see, you all proved your own point. Without your input, I'd be trying to get AvGas evrywhere for $5.50 a gallon and eventually it would have been such a pain that it would be an excuse not to drive it as much.

I did have a '67 Vette once, and AvGas DID make a difference. However, compression was an issue.

Thanks for the help. End of thread.

[niall]

Quote "2) 100LL has less lead than the old 100/130, hence the name "Low Lead", but has twice the lead of the old 80/87. That's a lot of lead for an engine designed to run on unleaded gas."

I never knew the 911 engine was designed to run on unleaded. Fuel containing lead is no longer available here and as my car is 1975 I just assumed it would need a lead additive if running on unleaded fuel. So I have been putting in lead additive with every fuel fill, as I run on unleaded fuel only.

So is it correct that lead additive may not be necessary anymore?

Niall

[billybek]

I believe that he means that the SC was built to run unleaded..
Your 75 on the other hand probably still needs a lead additive unless you have changed out the valves / seats to a harder material that would allow unleaded use.
Others most likely have more to say on this....
Crazy Horse, I hope your trip is uneventful!
I drove my "new" SC 3000 miles to get it home!
What a blast!!!

[Netspeed]

Running high-octane gas is a waste unless your vehicle has been timed for it. Engines ping because the gas is pre-detonating which is why modern cars have knock sensors (and a host of others) that retard the timing so the ping goes away. Retard the timing and you lose power. Unless you've specifically had the engine timed for the AV gas, you won't feel any difference. There's upper limits on how far you can advance the timing too and I'm pretty sure that the upper limit is right about what 95 octane fuel would produce.

Many modern cars are designed to run on lower octane. When I worked at the Chevy dealer (in service), customers would come complaining of poor running (usually in the trucks and suv's). It turned out they were putting 92 octane in it when they were designed for 87. I can't remember the exact reasons why they ran poorly, but even GM came out with a bulletin to address the issue.

[rusnak]

The only factory applied sticker pertaining to gas is the one that reads: "Unleaded Fuel Only" and it came on U.S. 911SCs in body color.

[Miguel Antonett]

No additives.

If any, some Techron for a highway tank of gas every so often.

[911s55]

What OTHER stickers are on your car?

[Crazy Horse]

Other stickers on my car:

1.) Check oil level with dipstick when cold and engine not running.

2.) Use only 30 weight Walmart brand oil

3.) Tire pressure 65 lbs

4.) ME-109