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Old 06-08-2006, 06:22 PM   #15
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My wife's BMW 740I gets 3 to 4 MPG better when running premium versus lower octane fuel. It is noticeable over a long journey although the actual costs incurred are up due to the use of the more expensive fuel. We do notice that the car "seems" to run better with the higher octane but that could just be me.

My TrailBlazer doesn't seem to notice a diff. It sucks it up regardless, get the same mileage, which is not very good at the best of times although surprisingly it's as good as my friends new KIA equivalent (heh, heh) which is a pain for him. When towing the TB gets horrible mileage, worse than my '57 Pontiac with a 455.

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Old 06-08-2006, 09:46 PM   #16
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An interesting thought, about 2 years ago, the gasoline pipeline from El Paso to Phoenix, Az. ruptured out in the desert, shutting down supply of gasoline to the city and surrounding area. Everybody was out of gas in every grade. Few people picked up on the concept that that one gas line supplied the regular, mid-grade, and premium to the city and all the vendors. One type of gas arrived at the batch plant. That gas was given anti-knock additives and detergents to make the various grades. Every gas station got their fuel from that one gas line. The base product was the same at the QuikyPiky as at Union 76.

For the record, one of the refineries here in Corpus Christi is set up to produce all of the gasoline for one of the major cities in New Jersey. Again, the QuikyPiky gets the same gasoline from the same source as everyone else in the city.
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Old 06-20-2006, 10:22 AM   #17
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Quote:
Originally Posted by Wabbiteer
.......
Minnesota has mandatory 10% ethanol and I loose 12% highway driving with ethanol blend so I'm sensitive to mileage...........
When I get out of state and my highway mileage of ~15mpg goes to ~17mpg with less oxygenators added (ethanol) ............. My mileage jumps to ~19+ if I ease back out onto interstate, blend smoothly and drive the tank empty. ............17 to 19 is nearly 12% so if the premium for premium is below 10% I can usually save money burning premium. At $2.80 a gallon for regular 87, 91 octane (ethanol free) for $3 would be a deal for me.
~
So am I correct in thinking that while towing ( esp at higher elevations), it would be wiser to go preimum over regular (assuming ethanol additive) for the extra oomph? Does anybody know of a state by state break down of ethanol additives? or has it become ubiquitious now?
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Old 06-20-2006, 11:18 AM   #18
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Usually unless your vehicle is E85 rated, the 10% ethenol mixture is the maximum blend you can run. I've not seen any station offer anything higher than 10%. The down side is that ethenol does not provide the equivalent mileage of pure gasoline, so it's not unusual to see that some premimum gas without the ethenol additive might give you better mileage.

As far as higher altitudes go, I think I remember at one time seeing higher altitude Colorado gas stations selling 89 octane as their low end product.

We have several oil terminals in the metro area and I have seen all brands of trucks show up there. From what I have been told the only difference between brands is the additives. In many cases the tanker trucks carry the additives and the mixing of those additives occurs during the tanker fill up. Other than that they are all buying the same base grade gas.

In my part of the state the environmental emission regs require that we use blended fuels in all grades during the summer months. Interestingly enough if I go 50 few miles east into Illinois many stations sell their ethenol blended mid grade (89 octane) fuel for up to $.05 per gallon less than the unblended (87 octane) regular.

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Old 06-20-2006, 12:21 PM   #19
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Ethanol raises octane - In Iowa I've seen they used to offer non-alcohol regular for up to a 10¢ premium over the mid-grade containing 10% ethanol, however with the MTBE additive ban the demand for using ethanol as replacement has driven the price up so the cost difference may be moot point these days.

Assume there is some ethanol in all gas, it acts as a drier via carrying it through water-excluding filters. There certainly is Ethanol in Premium gas, blended gasolenes include tolulene, benzene and a dozen other solvents depending on spot prices or availibility.

Its hard to find but Minnesota has a pure petroleum Super-Premium that is intended for off-road recreational vehicle use only. The product commands a steep price premium and is provided to maximize safety when our weather can become life-threatening whether in power craft on the water or winter time sports.

When last in Colorado I used the lowest octane (85?) as the prices where 30-40¢ higher then I'd just seen in Missouri and Kansas - definately slow on the spot-market price adjusting in Colorado from what I remember. I'm sure its all justified but sure looked like gouging to me...
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Old 06-20-2006, 12:28 PM   #20
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Quote:
Originally Posted by Wabbiteer
........Assume there is some ethanol in all gas, it acts as a drier via carrying it through water-excluding filters. There certainly is Ethanol in Premium gas, blended gasolenes include tolulene, benzene and a dozen other solvents depending on spot prices or availibility.....
Now I am more confused than normal . In an eariler post I understood you to say that the ethanol in regular gas was resulting in poorer performance compared to premium. Was I incorrect in this understanding, or is it simply a matter of the percentage of ethanol between grades?
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Old 06-20-2006, 12:39 PM   #21
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Quote:
Originally Posted by Wabbiteer
Towing my AS at 55mph and smooth higway driving gave me almost 14mpg using premium - I started calculating dollars per mile and saw a spread between $11 to $17 dollars per hour cruise with speeds & fuel octane changes. Hate being an obstacle in the right lane but money is too tight to be fuelish, just smile and wave like its great fun and get even at the fuel pump.
~
Hmmm. First trip with the Trade Wind I got about 8 mpg. Reading here I found out that 5th (or overdrive) is not my friend. Going to the midwest forums rally I kept it in 4th and right at 55 traveling mainly on state routes. Result: about 11-11.5mpg. If switching to premium would give some more power and boost me another 1-2 mpg, I would be a happy camper indeed.
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Old 06-20-2006, 12:41 PM   #22
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Quote:
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Does anybody know of a state by state break down of ethanol additives? or has it become ubiquitious now?
In Washington it varies by region. The Seattle area has the worst polution problem because of traffic density and the trapping of air between the Olympic and Cascade mountains. When we go on trips and fill up "out in the boonies" I regularly see 2mph increase (10%) over fuel in the Seattle area. The huge difference in efficiency makes me wonder if the added ethanol might actually increase polution.

Modern cars adjust the timing and fuel mixture based on the exhaust gas. OBDII cars don't even get "tested" when you take them in for emissions. They just hook it up to the computer and the car tells them how it's running. My old '86 Crown Vic that was originally a State Patrol car hates regular gas. The combo of dumb engine management and slightly higher compression makes it ping like crazy. That will destroy an engine in short order.

Aviation fuel has long been used by hot rodders and racers. Even with no road tax it commands a steep price premium.

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Old 06-20-2006, 12:55 PM   #23
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Quote:
Originally Posted by safari57
My wife's BMW 740I gets 3 to 4 MPG better when running premium versus lower octane fuel. It is noticeable over a long journey although the actual costs incurred are up due to the use of the more expensive fuel. We do notice that the car "seems" to run better with the higher octane but that could just be me.

Barry
Barry,

The 740I runs Motronic by Bosch, a truly adaptive engine management system. It occupies sensors for many different engine and ambient parameters. This vehicle does benefit from high grade fuel, as it will advance timing of spark plugs and injection depending on the sensor's inputs many times a second. The result is usually a smoother running engine, that has a crisper throttle response.
My 1997 Suburban is supposed to have a knock sensor, retarding timing to prevent engine knock under load when running regular unleaded gas. I have had the vehicle at Chevrolet several times, because there is a pronounced engine ping under heavy load when towing. This goes away when I run premium unleaded. Chevrolet says that there is no fault in my engine management system, and everything is as it is supposed to be. But still, I must run premium when towing, while it motors along quite happily on regular when not towing. However, there is no difference in mileage, or otherwise, when I run premium while not towing.
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Old 06-20-2006, 01:52 PM   #24
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Has anyone ever seen an engine that was destroyed by pinging? I keep hearing that pinging will destroy an engine in short order, but I never have seen one damaged in that way and would enjoy finding out what parts were damaged (in short order). Diesels work on the principle of predetonation and without it they wouldn't even run. Someone Please, show me pictures of a gas engine destroyed by predetonation knock. I want to see the bearings which were pounded flat, or the pistons with big holes burned in them, maybe a split or cracked valve or valve seat. Inquiring minds want to know (and see).

Personally, I think this was a phenomena which was seen prior to 1950 when engine parts and lubrication wasn't up to the very high standards we see today, but then I may be wrong. Predetonation could have lead to the demise of the Hudson, the Studebaker, the Oldsmobile or the Yugo. We need to see what we are so afraid of!

We need John Stossel set up two engines side by side on dynomometers, one set to ping and one not and run them until one fails and look at what happened. Also, it sound like a good test for "Myth Busters".
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Old 06-20-2006, 02:15 PM   #25
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Has anyone ever seen an engine that was destroyed by pinging? I keep hearing that pinging will destroy an engine in short order, but I never have seen one damaged in that way and would enjoy finding out what parts were damaged (in short order). Diesels work on the principle of predetonation and without it they wouldn't even run.
I'm far from being a mechanic but I was told that in a gas engine, the spark is fired just prior to the piston being at top of cylinder. By the time the force of ignition occurs the piston is at top and no damage occurs. It's all in the timing of the spark and the position of the piston in the cylinder. Spark or ignition comes too soon, and you get the effect of the explosion occurring and attempting to force the piston down, when in effect it is still on the upstroke. I've attached a picture of a damaged piston where preignition occurred.

Someone correct me if I'm wrong but doesn't the compression in a diesel engine actually trigger the ignition? I would think that the diesel would work on the same principal, minus the ignition spark. Its a high compression engine which generates the heat at high compression. The piston again would be almost at top when the explosion occurs. Obviously the glow coil provides the initial heat source until the engine heat is self sufficient to maintain the combustion.

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Old 06-20-2006, 02:17 PM   #26
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Quote:
Originally Posted by Bob Thompson
Has anyone ever seen an engine that was destroyed by pinging? I keep hearing that pinging will destroy an engine in short order, but I never have seen one damaged in that way and would enjoy finding out what parts were damaged (in short order). Diesels work on the principle of predetonation and without it they wouldn't even run. Someone Please, show me pictures of a gas engine destroyed by predetonation knock. I want to see the bearings which were pounded flat, or the pistons with big holes burned in them, maybe a split or cracked valve or valve seat. Inquiring minds want to know (and see).

Personally, I think this was a phenomena which was seen prior to 1950 when engine parts and lubrication wasn't up to the very high standards we see today, but then I may be wrong. Predetonation could have lead to the demise of the Hudson, the Studebaker, the Oldsmobile or the Yugo. We need to see what we are so afraid of!

We need John Stossel set up two engines side by side on dynomometers, one set to ping and one not and run them until one fails and look at what happened. Also, it sound like a good test for "Myth Busters".
I like the myth buster idea, Bob. They have the funds to pull of these things..and cameras!
I am amidst a engine rebuild on a 59 Mercedes 6-cyl. This engine has had it's share of pinging and clattering, and tehr eare no signs of damage on teh piston tops, or valves, or valve seas. Just normal wear.
A while back ( quite a while) I drove a 79 Buick "ping" Estate wagon..for a hundred thousand miles or so, the thing pinging just about all the time. It would run on after the key was off, like in a bad movie. It did not break for me, unfortunately. We eventually junked it because of other reasons.
So, I second your question on the real problem with engine ping.
My Suburban pings at certain times, as described in another post. My impression is that when the pinging starts, the perceived engine power drops a bit. But what else is happening?
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Old 06-20-2006, 03:43 PM   #27
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I did study Mechanical Engineering in College and one of the areas we studied was fuels, anti-knock compounds, and internal combustion engines. Based on the principle that compressing a gas causes it to heat to the point of combustion is what we're talking about. Diesels are based on this principle. Compression ratios of around 17:1 are required to get diesels to fire. A ping, or predetonation knock is the fuel firing because of compression. By adding anti-knock compounds, this firing can be delayed until the spark of the spark plug fires the fuel.

I do see some damage to the top of the piston, but it is in the form of scratches, gouges, etc. Since there is no way a piston ring could have caused this damage, it had to have been a valve or a foreign object which caused the damage. I've looked close and don't see damage caused by preignition. Perhaps someone can point out this damage for me. Are there minute stress cracks in the top of the piston which I can't see?

I have seen pistons with holes burned in them from running too lean and too hot, usually because of supercharging or turbo'ing. This is a case where someone has added an aftermarket device to artificially boost the compression ratio but didn't recognize the need to boost the amount of fuel to the cylinder so that the fuel air ratio was maintained at the correct proportion.

Our family had one of those vehicles which ran on after the ignition was turned off. It would set there and run and run and ping and knock and send out black smoke, and you just knew it couldn't be good. But the engine, like Uwe's lasted well past 130,000 miles, and it was other problems which eventually lead to it's end.
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Old 06-26-2006, 10:52 AM   #28
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Been looking and not finding

Does anybody know where to find a state by state (or by region) listing of ethanol added gas? Or is it just everywhere now?
thanks
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