Reg versus Premium Fuel experiament in 09 PT Cruiser

I don't know for sure, but there are those that would say that you have to give your PCM time to adjust to the different fuel to make a meaningful mileage measurement.

It should be down a little. Premium has less energy per unit volume.

That used to be true (say 30 years ago), but these days it is not ture.

Ed

I had a Neon RT. I did an extensive milage test early on. I did ten tankfuls of regular, then ten of premium, figuring the variance of each set. The milage with premium was down a little, but less than one mpg. However, the variance in each set of runs was over 1.5 mpg, so I had to conclude it made no difference.

I think the Neon engine was very similar to that in the PT (though mine had the DOHC heads).

If higher octane ratings are achieved through oxygenates it certainly will be lower because those high octane oxygenates have less energy/volume. I think it is highly unlikely that higher octane ratings would be achieved through aromatics these days for fuels one can buy at regular gas station.

High Octane has the same energy. It has a higher OCTANE and is wasted or may not be burned as completly in a low compression motor or with retarded or less advance in the timing of ignition. It burns slower and does not detonate under heat of compression as easily as regular. Fuel that uses more ethanol to increase octane has less energy. Regular fuel with ethanol has less energy. A 12 to 1 compression or even 14 to 1 compression motor burning 105 octane or higher will get better mileage and torque if the ignition curve etc are right. Just like diesel the motor has to be built for the stress. What we have now and for a long time is junk engines designed to be built as cheaply as possible and to run on junk fuel as per EPA or California really. The electronics are good at getting the most from junk. Just imagine what great engine structure and electronics would do with great fuel.

That's what I was thinking. I wonder how much alcohol they are allowed to put in basic gasoline. Maybe the main difference between regular and premium these days is the amount of alcohol they put in it.

I don't understand you claims of "junk" engines. Today's engines are far better in pretty much every way then everything that came before them including durability. That's a general statement, there will always be a few bad designs. Up until the mid/late sixties, engines were so weak that it was common for them to need valve jobs before

100K and for many of them they needed both rings and valves before that point. There used to be a thriving industry doing ring and valve jobs there was such a demand for it.

My preliminary assessment is that it's down at least 2 mpg and possibly as much as 3 or 4.

In our town, they can put up to 10% ethanol in the gas. I think it's some kind of scam the state is taking part in but that's the brakes. There is a slight drop in gas mileage but the good news is that I can use the lowest grade of gas in my cars without knocking. Previously, the cars had to use mid-grade.

They also finally figured out how to and/or decided to make CV joint boots that could generally last the life of the car. They had to replace those recurring multi-hundred $$ maintenance needs with something else. That's when some genius said "Hey! I've got it! Let's start driving the cams with timing belts in almost every engine, *AND* let's bury the water pump inside the engine and have it be driven by the timing belt! And to really mess up a few people's bank accounts, let's make those same engines with the cams driven by high-tech rubber bands to be interference!!". :)

Remember the Hemi of the late 60s, not the mid sixties. It put out an honest 800 hp and 860 ft lbs according to modern testing a year or so ago. They came apart because that much power and trying to rev past 8000 rpm. If you kept it at 7000 or below everytime it stayed together. However the head block gasket would seep a little bit of oil, if constantly stressed. Name me one engine that puts out that torque that you can afford. I've got one of the modern high hp jobs. It revs like crazy but hasn't got any torque. Next time you get a chance ride in a 70 442 w 410 gears, or a Hemi Cuda properly tuned. A 429 Cobra Jet or a 428 for that Matter, or a high winding 427 or a bunch more. The new engines don't come apart becaause they don't put out power that will break them. you 3.3 mph per second regulated electronic throttle is a wuse. A hemi with modern developments could probably push 900 hp. Street Rod Standards are now in the 1000 hp range. Try that with a Mercedes engine short of 6.3 twin turbo. None of them will survive. The reason the don't run 186 mph or above is rear gearing and no overdrives in the gearbox. A 440 or hemi and a number of others would do

155 at 8000 but don't expect it to live. Ride in a 427 Vette and wish it had the gearing etc box of the new Vette. The technology is far more developed today but it is not applied but who "needs" a 250 mph 900-1000 hp Hemi. The new Hemi is more a Polsphere head It has an unfinished area to hold heat and twin plugs to burn junk fuel.

But that has nothing to with the engine itself. To claim that burning rings and valves is evidence of a "weak" engine is silly. That definition would mean the weakest engines are the ones used in dragsters and race cars.

Take a hundred of what you think are the best built car engines today and install a breaker-point ignition and a carburetor on them and you'll find out the rings and valves don't hold up as well as the cars that were designed with those old fuel and ignition systems.

The point that I think was being made was that toady's manufacturers and oil companies are delivering cheaper quality to the consumer, but the electronics used today more than compensate for that.

-jim

dsi1 wrote in news:w4OHm.132$ snipped-for-privacy@newsfe20.iad:

Gas suppliers HAVE to add some oxygenate to meet emissions specs,and alcohol was the replacement for MBTE which was polluting the environment.

I believe non-flex-fuel vehicles cannot reliably tolerate much more than

10% alcohol without modification.

That is a lot! How many tankfuls and what is the variance of the test?

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From

"Conventional fuels always have varied in heating value. One cause is the formulation differences among batches and among refiners. A survey of 1990-1991 conventional gasolines found that the heating value of summer gasolines varied over an 8 percent range. Heating value also varies by grade and by season. On average, the heating value of premium-grade gasoline is about 0.7 percent higher than regular grade because premium grade, in general, contains more aromatic hydrocarbons, the class of hydrocarbons with the highest densities. The heating value of winter gasoline is about 1.5 percent lower than summer gasoline because winter gasoline contains more volatile, less dense hydrocarbons.

"Oxygenated gasolines (see page 53) have lower heating values because the heating values of the oxygenate components are lower than those of the hydrocarbons they displace. The percentage decrease in heating value is close to the mass percent oxygen in the gasoline. For example, in keeping with federal regulations, gasoline in carbon monoxide nonattainment areas in the U.S. is oxygenated to a minimum of

2.7 mass percent oxygen during four or five winter months. The heating value of the oxygenated product is about 2.7 mass percent lower than that of conventional gasoline. In addition, federal RFG and California Phase 3 RFG in federal RFG areas are typically oxygenated year-round to an average oxygen content of about 2 mass percent. The resulting heating values are about 2 percent lower than that of conventional gasoline. California Phase 3 RFG also has limits on distillation temperatures and aromatics content, which has the secondary effect of lowering the density of the fuel. These limits reduce heating value by about another 1 percent.

"The gasolines that produced the results displayed in Figure 1.3 were specially formulated to span a wide range of compositions. The compositional variations were much greater than those separating conventional and reformulated commercial gasolines. Thus, the results provide solid evidence that RFG does not exert an unusual effect on fuel economy. Individual drivers have reported decreases of 10 percent, 15 percent, and even 20 percent in fuel economy when they began using RFG. Not surprisingly, many of the claims are anecdotal. Most drivers do not keep continuous fuel-economy records, so they don't have a meaningful fuel-economy baseline for the gasoline they previously used. Even with a baseline, a fuel-economy value based on the consumption of a single tank of gasoline can be misleading. Drivers interested in fuel economy should average results over several tanks of gasoline or, better yet, over several months of driving."

From

: "Gasoline with a higher heating value (energy content) provides better fuel economy. Traditionally, premium gasoline has had a slightly higher heating value than regular, and, thus, provides slightly better fuel economy, but it is difficult to detect in normal driving. There can be even larger differences in heating value between batches of gasoline from the same refinery, between summer and winter volatility classes, or between brands of gasoline from different refineries because of compositional differences. The differences are small and there is no practical way for the consumer to identify gasoline with a higher-than-average heating value."

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I saw some of that on my own. it's just longer ways of saying the same thing and some additional detail. RFG has been around for 14 years now. Even when I've been out in the middle of no where, well outside the RFG mandated areas (

) the fuels have at the very least contained ethanol if not fully RFG compliant. Do any refineries make anything else now? (I thought ethanol was a federal requirement anyway) Once adding that stuff the easier way to higher octane is just putting in more of it.

Now you're just being silly. Talking about 800 hp engines the comprised 0.002% of the market is meaningless. In the 60's your primary engines were the Chevy and ford 6's and small block v8s and similar in the upscale cars like Buick, Lincoln, etc. Not only the engines but the cars themselves were often worn out within 10 years/100K miles. If you want to talk about power, consider that back in the day a typical 6.6+ Liter muscle car might do 0-60 in 6.6 seconds, I forget their quarter mile numbers. My 99 GT with 4.6L motor can do the same 6.6 and quarter, more or less. And instead of getting 13 mpg I can get 18 mpg or better. Heck, people with new Corvettes that will blow the doors off the Corvettes from back in the day, have reported 30 mpg on trips. You are living on some other planet if you believe what you are writing.

I suppose we could split hairs over the quality of the lock washers too. It is what it is and is what it was. Today's clearances are much tighter, the engines are cleaner burning, etc. Sure, if you want to take a complete system (today's engines) that was designed for today's technology, and remove part of it and substitute parts it was never designed to use, sure, you can make it worse. Next you be singing the praises of wooden wagon wheels over modern tires because the wooden ones never blew out from being run low on air.