the deal on premium/mid grade gas

[Heyupduck]

OK, lots of oil people here. Can somebody who knows give me a definative yes or no about whether there is any benefit to putting mid grade gas 89 in my engine
My engine manual says to use 87

If I'm going over the mountains I put it in, now gas is cheap I might top off the tank with it to give my engine a treat (which is kinda stupid maybe because I have no evidence to go on other than the higher cost)

Thanks in advance

[rugatika]

http://www.caranddriver.com/features...results-page-2

Our tests confirm that for most cars there is no compelling reason to buy more expensive fuel than the factory recommends, as any performance gain realized will surely be far less than the percentage hike in price.

[Bohuntr]

with the computers in vehicles today the recommended octane is what you should use as the car is programmed for that octane. you actually will get worse mileage with some vehicles by going to higher octane.

[CowichanBay]

Originally Posted by rugatika

http://www.caranddriver.com/features...results-page-2

Our tests confirm that for most cars there is no compelling reason to buy more expensive fuel than the factory recommends, as any performance gain realized will surely be far less than the percentage hike in price.

+1. Unless your vehicle specifies premium, save your money.

[Buckhead]

It depends on the vehicle, the compression ratio and which spark (timing) advance tables are programmed into the ECM.

Some vehicles will slightly advance the timing if you use 89 octane giving you a bit more horsepower and mileage.

The only way to know is to try it. If you want to do a cost/benefit analysis to see if it is really doing anything worthwhile for the extra cost - fill up 3 tanks with regular (87) and keep track of the kms driven and total cost. Do the same with the 89 - then calculate the cost per km driven.

That will help you decide.

Just topping off the tank isn't really going to tell you anything.

[Bobby B.]

The difference in the three grades of fuel at the pump is the amount of octane. Octane is linked to compression. High compression engines require high octane amounts. The higher the level of octane, the higher the compression can be without the fuel detonating prior to ignition.

Bobby

[roger]

Putting synthtetic oil, a new air filter (aftermarket or factory )and correct tire pressure is likely to provide higher dividends.
Even washing the vehicle and keeping excess mud/snow buildup of the vehicle helps. Cary ing a few hundred extra pounds for long distance is a pointless cost in mileage.
maybe add a can of injector cleaner...but im on the fence with those things.

[Tactical Lever]

The additives in fuel to give it a higher RON or anti (?) knock index are usually ethanol or other additives that are lower BTU than gas giving less energy (or change the burning profile). If your vehicles needs it however it will be fighting itself or compensate with retarded spark timing as it senses knock and put out less power and mileage.

Very few (excluding sport machines) benefit from decreased volatility.

[Rockyman41]

One benefit of some premium fuels is that they contain no ethanol. If you have a second vehicle or one that sits for long periods of of time the ethanol in regular fuel can absorb water and potentially cause rust inside your fuel system.

Ethanol hurts your fuel mileage as well. If I remember correctly it's approx 5% decrease in mileage for every 10% of ethanol. Im not sure the higher mileage would offset if the added cost of premium.

[Canehdianman]

No.

[Big Grey Wolf]

Ethanol does not hurt your mileage! Ethanol has a RON of 130 octane. It is one of the best octane additives you can add to gasoline. You do not require higher grade gasoline in 99% of cars and trucks. Only vehicle might be a older corvette with high compression engine. Only benefit of higher octane gas is to the oil company, they can charge 10 cents a litter more for it.

[bloopbloob]

Originally Posted by Big Grey Wolf

Ethanol does not hurt your mileage! Ethanol has a RON of 130 octane. It is one of the best octane additives you can add to gasoline. You do not require higher grade gasoline in 99% of cars and trucks. Only vehicle might be a older corvette with high compression engine. Only benefit of higher octane gas is to the oil company, they can charge 10 cents a litter more for it.

Lots of vehicles benefit from higher octane. It all depends on the tune/timing. If properly adjusted for the octane, you will see a performance gain. Timing can be advanced further without pre-detonation. If you expect that just switching from 87 to 91 or higher, is going to add performance gains, the truth is, that you will actually see less power.

[Peace Meal Farm]

Previous posts about fuel knock, octane ratings and spark timing are all bang on. There is no real need to run high octane unless your compression ratios warrant it, and modern relatively low compression engines will not retard the timing enough to give massive power benefits.

The argument for avoiding ethanol is strong. Ethanol contains less carbon than conventional gasoline blends and as such does not offer as much energy when it is burned. Higher ethanol content does hurt fuel economy.

Flexfuel vehicles which are designed to run on high ethanol blends significantly richen the air:fuel mixture when high ethanol is used. With ethanol stoichiometric ratio is no longer bang on at 14.7:1. This has lead to the requirement (heavy use?) of wide band oxygen sensors, which no longer give feedback in traditional voltage pulses but instead give feedback against a variable definition of stoich. Interesting stuff!

When dealing with small engines and older vehicles the case to avoid ethanol is strengthened. The hygroscopic nature of ethanol leads to an increased 'moisture content' within the fuel. This takes out metal fuel tanks, lines etc etc. There is a reason that all of the new stuff coming out has plastic fuel systems.

[elkhunter11]

Originally Posted by Buckhead

It depends on the vehicle, the compression ratio and which spark (timing) advance tables are programmed into the ECM.

Some vehicles will slightly advance the timing if you use 89 octane giving you a bit more horsepower and mileage.

The only way to know is to try it. If you want to do a cost/benefit analysis to see if it is really doing anything worthwhile for the extra cost - fill up 3 tanks with regular (87) and keep track of the kms driven and total cost. Do the same with the 89 - then calculate the cost per km driven.

That will help you decide.

Just topping off the tank isn't really going to tell you anything.

Exactly, there is no one answer that covers all vehicles. Some of the modern computers will advance the timing to take advantage of the higher octane, and the engine will perform better and produce more mileage on a given amount of fuel. On other vehicles, the computer is not capable of doing this, and the engine will not benefit from higher octane fuel. The only way to know for sure is to test fuels with various octane levels in your vehicle. I always use the highest octane fuel available in my motorcycle, and the difference in fuel mileage is very noticeable between 87, 91, and 94 octane. The difference in my car and truck is slow little, that I just use 87 octane fuel.

[elkhunter11]

Ethanol does not hurt your mileage

The tests don't agree. Ethanol contains less energy, and it produces less fuel mileage. The more ethanol the fuel contains, the less fuel economy the vehicle produces.

http://www.edmunds.com/fuel-economy/...ison-test.html

http://www.consumerreports.org/cro/2...bate/index.htm

http://www.caranddriver.com/features...economy-page-7

[Rockyman41]

Originally Posted by Big Grey Wolf

Ethanol does not hurt your mileage! Ethanol has a RON of 130 octane. It is one of the best octane additives you can add to gasoline. You do not require higher grade gasoline in 99% of cars and trucks. Only vehicle might be a older corvette with high compression engine. Only benefit of higher octane gas is to the oil company, they can charge 10 cents a litter more for it.

Isn't your statement a little contradictory? First you state ethanol is good because it's octane rating is 130, then you state that higher octane fuels only benefit the oil companies.

Straight gasoline has an energy density of about 110-115,000btu/lb ethanol is around 75,000. So ethanol has roughly 65-70% of the energy of gas. Less energy requires more fuel and elkhunter11's links show that.

[pinelakeperch]

If your driver's manual calls for it, or if there's a small sticker in your fuel door that recommends premium, put in premium. If it doesn't, you'd be wasting your money. This has been discussed ad nauseum.

[Selkirk]

Originally Posted by jhutter

If your driver's manual calls for it, or if there's a small sticker in your fuel door that recommends premium, put in premium. If it doesn't, you'd be wasting your money. This has been discussed ad nauseum.

So true ^

But it's still sad to see how many people ignore this, and buy mid and/or premium gas for their vehicles that are specifically designed to burn regular.

Their money would be far better spent, donating it to a good charity.

Mac

[amosfella]

A lot of the European made vehicles require premium gasoline. When I was over there, standard fuel was 92 octane, and premium was 95. I drive a european vehicle, so I use premium. If I put in regular, fuel mileage creeps down as does performance...

[elkhunter11]

Originally Posted by amosfella

A lot of the European made vehicles require premium gasoline. When I was over there, standard fuel was 92 octane, and premium was 95. I drive a european vehicle, so I use premium. If I put in regular, fuel mileage creeps down as does performance...

Europe uses a different octane rating system, so their octane ratings are always higher.

[pinelakeperch]

Originally Posted by amosfella

A lot of the European made vehicles require premium gasoline. When I was over there, standard fuel was 92 octane, and premium was 95. I drive a european vehicle, so I use premium. If I put in regular, fuel mileage creeps down as does performance...

Simply driving a "European car" doesn't mean you need to put in premium fuel. There are 300+hp Volvos that run on 87 octane.

[amosfella]

Originally Posted by jhutter

Simply driving a "European car" doesn't mean you need to put in premium fuel. There are 300+hp Volvos that run on 87 octane.

You'll notice that I said 'A lot of European vehicles'. The one I use requires premium.

[pinelakeperch]

Originally Posted by amosfella

You'll notice that I said 'A lot of European vehicles'. The one I use requires premium.

You specifically said, "I drive a European car, so I use premium", as if implying by virtue of a car being European, premium fuel is necessary.

[elkhunter11]

Originally Posted by jhutter

If your driver's manual calls for it, or if there's a small sticker in your fuel door that recommends premium, put in premium. If it doesn't, you'd be wasting your money. This has been discussed ad nauseum.

That is the minimum suggested octane, that doesn't mean that the vehicle will not perform better or get better fuel mileage with high octane fuel. Some engine management systems are capable of improving performance with higher octane fuel, and some are not. The only way to know for sure is to test fuels of different octane ratings in your vehicle.

[pinelakeperch]

Originally Posted by elkhunter11

That is the minimum suggested octane, that doesn't mean that the vehicle will not perform better or get better fuel mileage with high octane fuel. Some engine management systems are capable of improving performance with higher octane fuel, and some are not. The only way to know for sure is to test fuels of different octane ratings in your vehicle.

Yes, but a manufacturer isn't going to suggest an octane rating if a different one will produce significantly better results. Plenty of independent tests have been done, and the verdict is that the extra cost in many cases isn't worth it if the manufacturer doesn't recommend it.

With regular fuel being ~ $.75/l and 91-94 oct being a 20 cent premium over regular, you're spending an extra $12 per tank in a 60 litre tank. That $12 would buy you a quarter tank of gas at those prices. In other words, you would have to experience improved mileage of > a quarter tank using premium to make that route make sense. Frankly, that isn't going to happen.

As far as improved performance, as a person who has owned and spent time with performance cars, if they didn't require premium for the factory (and haven't been modified for performance), the performance increase is going to be negligible.

[Tom Pullings]

Total rip off for the average vehicle that specifies 87.

[elkhunter11]

Plenty of independent tests have been done, and the verdict is that the extra cost in many cases isn't worth it if the manufacturer doesn't recommend it.

The key phrase being" in many cases" ." Many" does not mean "all", so that means that in some cases, a higher octain fuel may increase performance or fuel mileage significantly. This is exactly why I mentioned testing fuels with different octane ratings in your vehicle.

As well the recommendations in most manuals state that the engine is designed to operate on gasoline with an octane rating of 87 octane or higher. or with gasoline with a minimum octane rating of 87. Nowhere does it state in my manuals that the vehicles run best with 87octane gasoline.

Yes, but a manufacturer isn't going to suggest an octane rating if a different one will produce significantly better results.

Actually there is a reason for doing so, they don't want people thinking that they will have to use high octane fuel to obtain the best performance, even if it is true. They know that some people would choose another vehicle, if they thought that the vehicle would not run at it's best with 87 octane gasoline.

[amosfella]

Originally Posted by jhutter

You specifically said, "I drive a European car, so I use premium", as if implying by virtue of a car being European, premium fuel is necessary.

I guess I could have been clearer on that one. I use a vehicle that specifies premium fuel...

[schmedlap]

of all this. I only know about long experience. After they took the lead out of regular fuel back in the early '70's, the older higher performance and big block V8's definitely needed premium to run without knocking themselves to death, and even after they then took the lead out of premium that was still the case. My '69 Coronet (318) and '72 Caprice (400) had to have at least 50% premium to run smoothly and with any performance. All of such were carbureted, of course.

The 2 '70's F250's with 460 V8's that I had (and I think those engines wer pretty "low compression"?) were fine with regular at most times, but if I was hauling heavy (camper and/or boat, and/or gear and people), or traveling at higher elevations, or up a lot of big hills, I soon learned that premium made a huge difference in performance and mileage. In fact, for those old enough to recall, Mohawk (and Husky?) were the only ones with ethanol blended regular for some years, and I seem to recall it had a higher "octane" rating (?), and I do know those trucks ran way smoother, better performance, and better mileage (well, 11 mpg is better than 9 on those beasts?) on the Mohawk gas than on the others. And I never needed to worry about putting in gas line antifreeze.

On all the newer vehicles (fuel injected) that I have had over the years, whether Japanese or American (4,6, or 8 cylinder, cars, SUV's, and trucks), all "rated" for 87 octane, I have never seen the same issues, at all. Premium gas, with or without ethanol blending, just does not seem to produce any advantage or necessity, regardless of the driving circumstances. So I tend to think any advantage of higher octane fuels ("mid" or premium) is really a non-issue and nonsense, with the perhaps exception of some high performance vehicles that are produced with that specific requirement (?).

[Deo101]

It's been said but I"ll repeat Octane Rating=Resistance to detonation. So if you don't have a high compression ratio you're wasting your money. It is actually less explosive. I was sure the purple gave me more power in the old 67 352" Of course newer vehicles ecm's will compensate for this but all in all is a waste of cash.