TheSamba.com :: View topic

Thu Feb 24, 2005 10:44 pm

i was reading in the manual for type 3's and it recomends 91 which is what i have been using. is this really needed? i am running a 1600 dp stock, with baby webers, header, and A-1 muffler. thanks!!

Thu Feb 24, 2005 11:02 pm

I run 91+ octane fuel in all my cars, but as long as it is properly tuned I don't think that it's necessary.

Thu Feb 24, 2005 11:13 pm

in my bug which was a sp1600 i used 87 and had no problems. maybe when i am close to empty i will give it a try and see if it runs hoter and take a look at the plugs before and after. i don't really have a problem with running 91 just wondering what others here are running in their type 3's and do you notice a difference from brand to brand?

Thu Feb 24, 2005 11:26 pm

karfer67 wrote: ...do you notice a difference from brand to brand?
Not really, but I try to avoid blended fuels, or fuel made from ethanol. No personal experience but I hear it's not the best stuff for your engine. Only good ol' petroleum-based fuel for my baby!

Thu Feb 24, 2005 11:46 pm

well mind telling me where you go? currently it has been am/pm because it is cheap and seems to run well.

Fri Feb 25, 2005 12:17 am

I use 91 in the notch, I have used 89 and it just dosent seem to have that extra kick that feels like a fresh tune up. I have heard it also keeps your dual carbs (or injection) clean, but I dunno about that.

when you change to lower grades of gas, make sure you listen for ping. I've even heard the term inaudible ping being trown around. lower grades may cause detonation, retarding the timing may or may not help. I think I have also read that when traveling in mexico where the quality of gas isn't as good, you may need to retard the timing.

Fri Feb 25, 2005 12:19 am

ah screw it i will just keep running 91 like i have at 2.17 a gallon. guess that is not that bad .

Fri Feb 25, 2005 3:41 am

By the way, the fuel octane specs given in the manuals usually are the RON spec, not the averaged R+N/2 spec that the gas pumps nowadays have on them. How they determine octane is sort of a complicated discussion, but in general terms, you can usually convert the old spec to the new by dropping it about 3 or 4 points. Different refineries gasolines can actually make a slight difference too, as the chemical mixture that results in a given octane number can vary from place to place. The true test is to listen and feel how the car runs on lower octane. Any knocking/pinging and move up. Knowing your car's compression ratio also helps too.

andy

Fri Feb 25, 2005 10:28 am

The spec in the owner's manual (and on the gas flap in newer models) is in RON, which is Research Octane Number, and is the way Europeans posts octane on their gas pumps. Another common test for octane is called Motor Octane Number, which always produces results which are lower than RON, typically 8-12 points for most gas used in cars on the road in the industrialized world. The US measure is to average these two numbers. So, 91 RON using the US measure would be about 85-87.

Thus, using US regular is fine in your stock Type 3. An engine built to have higher compression than stock MAY need to use mid-grade or premium. If your car doesn't ping on the gas you're using now, you're fine. Using higher octane doesn't cause any harm, so if using premium makes you feel better, no worries.

Fri Feb 25, 2005 11:12 am

well right now i am running 91 when it gets real low i will toss in 5 bucks worth of 87 and see what happens.

Fri Feb 25, 2005 4:40 pm

Mr. Bubblehead wrote: karfer67 wrote: ...do you notice a difference from brand to brand?
Not really, but I try to avoid blended fuels, or fuel made from ethanol. No personal experience but I hear it's not the best stuff for your engine. Only good ol' petroleum-based fuel for my baby!

I run strictly ethanol in ALL my VW's. In fact in all my cars. Gas milage may be a little lower, but the octane here is 89.5 and is $.05 cheaper than straight petroleum gas.

Fri Feb 25, 2005 8:07 pm

Ethanols of today are fine as long as it does not sit for long durations