Gas mileage

So my little trip to NC over the weekend I netted about 18.5 straight HWY. 2 years ago the same car same luggage etc, got 20.5 hwy.
Difference is about 25K more on the car but with a new opti now.

I'm thinking it's time for new plugs (coppers with almost 50K on them).
maybe the cats are getting clogged (180K on the car now)


thoughts??? as the car is going to Austin TX in 2 weeks (2700 miles RT).

2 years ago we were still running conventional gasoline. Now everything is E-10 which is good for a 10-15% decrease in MPG

Let your wife drive, maybe she has a lighter foot.

Tom

Id guess plugs, wires, maybe air cleaner, fuel filter... etc. My caprice averages 22-25 on the highway, even with the windows open.

my wife WAS driving, lol!!!

just put a new opti in about 500 miles ago. wires are only 50K old. plugs are NOT platinums but copper. think they aren't hot enough.

I hear you on the E10 crap but I was running that 2 years ago, on the same trip (the one where the CAI DROPPED my mpg by 2.....

I really think it's the crappy copper plugs not burning all the fuel and the O2s dump more in for the oxygen they see......

Pull the plugs and look at them. LT1 plugs are easy to get to whether from the top or through the wheel wells.

Check the gap and see if all of the edges have been worn off. If the gap is significantly more than the factory spec of 0.050", replace them. Also, if all of the sharp edges have been eroded off by spark, you could gain a bit by replacing them, as sharp edges promote a good spark.

If the plugs are too cold, then you'd see a lot of crud buildup on them. If not, keep running what you have as a spark plug running too hot is a prime source of pre-ignition.

the O2's made the biggest difference to gas mileage for me,.

a decent cai,.
with cats i,ve found they don't clog unless they,ve been overheated,.they become less efficient over time,.
fuel mileage can be varied with terrain,. wind ,. temps etc,.
i get better fuel mileage running premium fuel,.with the cruise off.

Nick

Quote :

i get better fuel mileage running premium fuel

That's because 87 and 89 have 10% ethanol, while 91/93 do not. It is such a scam.

Krzdimond wrote:

2 years ago we were still running conventional gasoline. Now everything is E-10 which is good for a 10-15% decrease in MPG

I wish you guys would stop whinning about the use of ethanol in gasoline. Thats not the problem. The fuel companies have been using ethanol as a cheap octane booster since they outlawed tetra ethyl lead back in the 70s. They are just advertising it now to show us how "green" they are.

The difference in heat value between straight gasoline and E10 is less the 3% (33018 BTUs/liter for gasoline and 31951 BTUs/liter of E10). Not saying it doesn't have some effect, but not 10 or 15%.

There is something else going on here. Back in the late 70s, Sunoco sold 110 octane fuel that contained almost 20% ethanol and in a high compresson (10:1) Pontiac 455, my fuel mileage did not change between 103 (high test) and the Sunoco Gold (110 octane). Could run more advance but no mileage change. On occasion, I had the opportunity to run leaded aviation fuel and again no discernable change in mileage, just had to change the plugs more often.

I suspect it's something else that is coincidental to the marketing of E10. With the EPA on its current "heavy metals" kick, its possible that some of the aeromatics are being removed, lowering the heat value of the fuel. We are seeing this in the new ULSD spec for diesel fuels. ULSD is now down to close to 34000 BTUs/liter. It could also be how the computers are set up when faced with the exhaust from ethanol blend fuels. Would be interested in finding out how well the new "flexfuel" vehicles react to the various blends.

Bill

Bill, while I agree that ethanol has been used for years (remember gasohol?), I haul the stuff and when I load E-10, on a 3000 gallon compartment, 300 gallons of ethanol and 2700 of no-lead. Premium (93oct) here is 10% corn, 50% (or so) no-lead and 40% premium. I can get the Bill of lading and post with the breakdown.......

We also have what's called "marine midgrade". Non ethanol conventional 89oct. I get a consistent 278 miles until the light comes on with the 89E-10, while with the marine midgrade, I get 315 to the 1/4 mark. Sounds like a difference to me.

I understand the math and the science between the 2 fuels. But there are SO many variables to consider, like plugs, compression, filters, line condition, pump condition and computer setup.

Now, while I do not fuel up from a metered pump, topped off is when I can no longer fit any more fuel into the neck.

Robert:

I fully understand the confusion. Its better up here as the consistancy, fuel pump to fuel pump, seems to be better. What Jay was refering to was the label on both our regular and mid grade fuels that state: "may contain up to 10% ethanol". The stuff labeled "ethanol" is actually E10 and is 89 octane. Since they restricted the use of MTBE in most jurisdictions, ethanol is being used more and more for octane, unless they have found some other witches brew that is cheaper. ETBE, isooctane and toluene are turning out to be just as dangerous and are significantly more expensive then ethanol.

My point is where are these mixtures calculated? At the refinery or the distribution center? Its very possible that the various grades are delivered to the tank farms with various levels of ethanol to meet octane levels and then mixed at the distribution points to reflect the stated ethanol quantities as per your exposure.

I find fuel (gas or diesel) much more predictable up here in Canada. Haven't had a bad batch in years. Can't say the same thing when I drive south of the border. Have had lots of problems, especially in the southern states, mostly with diesel but got a tank of gasoline two years ago in Georgia that went through the engine like *&^*&&% through a goose and the beast ran like hell. Next tank and problems cleared up. Now make it a point to fill up only at name brand stations, Exxon, Mobile, BP (not any more) etc. and when possible at high volume stations.


I do agree. Theres something else going on here and I suspect with our computer controlled cars, alot of fuel related problems are probably being masked and only manifest themselves in fuel mileage. Ergo my interest in the programming associated with the "flex fuel" cars that can detect ethanol concentrations and adjust accordingly. Running the correct timing and fuel delivery should more then compensate for the 3% drop in energy.

Bill