Is there any need to run my 73 2.0 on any gas higher than the regular 87 octane? I have heard that older cars run cooler when burning the highest octane possible?

IMO w/ the compression on these cars somewhat low, i run 87 and have never seen a difference w/ the premium. Ive had high compression v8's and such where they wouldnt run on 87. Save some money, use regular.

QUOTE (Gearren @ Jun 28 2005, 07:53 AM)

Is there any need to run my 73 2.0 on any gas higher than the regular 87 octane?

no.

if it pings, run midgrade until you can reset your timing to spec.

A '73, no. A '70-'72 1.7, yes (needs premium, has a higher compression ratio).

The whole "runs cooler" biz is a myth. Run the lowest octane you can w/o pinging.

QUOTE (lapuwali @ Jun 28 2005, 07:35 AM)

The whole "runs cooler" biz is a myth. Run the lowest octane you can w/o pinging.

"runs cooler" kind of depends on whether the car is pinging. Pinging will cause a lean condition when the correct combustion event occurs. A lean motor will run hotter.

So if you aren't pinging it won't effect the temp of your car. If you are pinging it could make your car run cooler.

I have to run premium in my '70 1.7L otherwise it starts pinging.

-Britain

I run plus or premium chevron only...
I could get away with 87... but I dont care... lol

Uuhhh... the factory wants us to use middle grade, says so, right there on the car.



M

One of the biggest issues out there right now is the use of oxygenated fuels. These fuels primarily are "premium grade" and contain ethanol or MTBE (Methyl Tertiary Buterol Ether) This is an oxygen bearing compound when burned release a molecule of oxygen for "clean burning" The main problem is it CAN and WILL cause the mixture to lean out. GM has a current TSB regarding it's use in all of the Vortec motors. "use of this fuel can contribute to a hot idle miss". My company recommends it's use, but says "if any driveability issues occur, discontinue using fuel containing Ethanol or MTBE." This is in the owners manuals. Which are never read, in my opinion.

However, you must also realize the EPA lists MTBE as a known carcinigen, so as we clean the air with our MTBE fuel, we contaminate everyone breathing it.

Lapi is right, Use only the grade high enough so as not to let the motor ping (detonate). This is primarily affected by timing and air/fuel ratio. Higher octane will only make a change in the engine characteristics when the timing AND mixture have been altered to work in conjunction with it. Also be wary of certain stations, even if it says 93 octane on the pump, In the immortal words of Mr F. Gump, You never know what you gonna get.

Erik Madsen

QUOTE (redshift @ Jun 28 2005, 10:53 AM)

Uuhhh... the factory wants us to use middle grade, says so, right there on the car.

Where? My 74 2.0 says "91 RON/ROZ" on the fuel tank's expansion chamber. 91 RON is equivalent to 87 US pump octane.

--DD

Yup. There's much confusion over the RON/ROZ v. the US octane measure. RON (Research Octane Number) and MON (Motor Octane Number) are two different ways of measuring octane, and the same fuel will USUALLY read about 9-11 points lower in MON than RON. In Europe, they use RON on the pumps, in the US, they average RON and MON. 91 RON + 81 MON / 2 = 86 (R+M)/2. In Europe, premium is 98 RON. When I bought by Squareback, the PO insisted it needed premium, as the sticker on the gas flap says 91 RON. I've put nothing but 87 in it, with nary a ping, and I expect I could probably put 80 in it with no problems. Third world car.

Octane available at the pump also varies from place to place. In CA, the grades are 87/89/91, typically. In the Midwest, 86/91/93 was commonly seen. At altitude, regular is often 84 or less, and premium may be only 89.

MTBE was used extensively in CA for years, but has been mostly phased out. Ethanol is the oxidizer usually seen these days here.

QUOTE (Dave_Darling @ Jun 28 2005, 03:59 PM)

Where? My 74 2.0 says "91 RON/ROZ" on the fuel tank's expansion chamber. 91 RON is equivalent to 87 US pump octane. --DD

I thought that was 89.





M

in my experience with aircooled motors, they do run a little bit(if noticable at all) cooler. They also seem to run better. I get better gas mileage on the stuff too. Did a test in my bug that had a 1.8 with dual 40 webers. Crap mileage and power on cheap stuff(chevron only), decent mileage and better power on 92. you wont notice a difference if you don't typically "drive spiritedly." At least not the power gain. IMHO

I don't know for sure but I think you have better gas down south than we have up east (less additives than what we get), or the folks have in Cali, I always ran 91 or 93,

I believe that it varies by station as well,

FYI- out here gulf, citgo, mobil/exxon all use MBTE, SUNOCO and Shell do not, so I always try to stick to either of them.

-I guess the guys who can hear the pinging must have really quiet cars, because there ain't know way I could hear that over all the other noise...maybe I'm just going deaf...maybe too many miles in the car with the top off...