can high test hurt?

All of the post 1985 Fords I have had liked 87 octane better than anything else. I have had better performance and better mileage. Another problem with the hiogher octane is the tendency to produce a bit more carbon contrary to what the ad folks would like you to believe. Ford recommends that you do not use higher octane. The only thing you get with higher octane if the engine doesn't need it is a lighter wallet.

Lugnut

I get about 1 MPG better with 86 octane vs. 87 octane in the Taurus.

Rob

If you do not have a high compression engine, you are probably getting worse performance from running the higher octane gas. The octane rating is actually a knock rating, "The ability of a fuel to resist knock is specified by the fuel's octane number. A fuel with a high octane number is more knock resistant". Higher octane burns slower not "better"...

Did he give any reasoning WHY he bought high test?

WHY are you using High test if your vehicle recommends regular?

Just use Bronze.

What's the worst that could happen?

Your previous owner friend is an idiot.

I have only had one Ford that called for reg in which I had to run high test because it ran better on it. Well it was my wife's van with a 351, and she used Sohio (Standard) gas, later BP. Or "Amoco" if you wish...

Turned out that when I finally convinced her to stop using that crap, it ran just fine on regular gas from anywhere else. (Note that BP recently started using the Amoco blend instead of its "own" and I have used it several times since with good luck, or no BAD luck. Before that, I would have had to run out of gas with no choice before I let it in my tank)

Buy the most popular brand, from an always busy station. I can vouch for Speedway/Marathon if it's popular in your area.. if not, dont use it.

I have had injectors checked at 150kmiles and they were almost whistle clean, required one cleaning pass, only. And never had a filter clog... even at over 75kmiles.

bg_jr. wrote in news: snipped-for-privacy@4ax.com:

The octane rating is the number given for the resistance of the gasoline to ignite. The higher the rating, the harder it is for the gasoline to burn. Your engine may knock if you are using a lower octane rating than is recommended by the manufacturer. Also, as an engine ages carbon tends to build up within the combustion chamber to the point that it increases the compression ratio. Therefore, older engines sometimes have a tendency to knock when burning the recommended fuel octane. The reason for the knocking is that the fuel/air mixture is igniting too EARLY. Engines are designed (compression ratio/timing) for a specific octane rating - it is typically a HUGE waste of money to use a higher than recommended octane rated fuel.

Therefore, the easiest answer to your question regarding the proper octane fuel to use is to use the octane rating as close as possible to what the manufacturer suggests for the engine. This mindset assumes you have not made major modifications to the engine (compression ratio/timing).

Yet another $.02 worth from a proud owner of a 1970 Mach 1 351C (searches for the highest octane I can find) @

You have it close, but not QUITE accurate. Octane is not specifically related to how easy fuel lights or burns. It has to do with how easily it "detonates" - or auto-ignites. Volatility and flashpoint, although peripherally related, do not determine octane. AKI, or Octane, has more to do with the hydrocarbon makup of the fuel and the chemistry involved in combustion - things like free radicals etc which cause UNEVEN burning of the fuel under high pressure and temperature, AFTER it has ignited.

The carbon buildup causes problems for 2 reasons - increased compression pressure, which requires higher AKI (anti knock index - or octane) to prevent detonation, and pre-ignition due to hot spots on the carbon lighting the fuel before the spark fires.

First, thanks for all the replies. Even though my friend was called an idiot, it is what I expect from some NG poster's, I guess for some it is too easy just to post the info without flaming, no matter.

I admit I was using high test because of "my" lack of knowledge and it is a shame that it took me all this time to finally wake up.

I have been using regular now, 87 octane rating, and I am having no problems. No pre/post-ignition, whatever it is called, good acceleration and fine idling. Matter of fact it seems to be runnng better, if that's possible. As far as gas mileage goes, I have been getting 23 in the city and expect that to stay the same.

So, thanks again for the replies and good information.

See, you_can_teach_old_dogs_new_tricks.

bg_jr. wrote in news: snipped-for-privacy@4ax.com:

;)

Meaning your friend fell for the marketing hype, of course.

Whatever your opinion of this 62 yo geezer's comments, take it to the bank that my other anecdoatal advice is on the level.

And yes, I am still learning new tricks, as well.

I still know people who will not buy anything but Shell or BP because they are the national brands, and thus must be 'better'

Of course they ALSO use Pennzoil and Fram... search around on the net for opinions on THOSE big names! I mean by people who actually KNOW something.

also lower octane fuel has more energy potential. more btu's released from regular than in higher grades.

This may SOMETIMES be true, but it is not necessarily so. A hightest fuel can provide the same BTUs as regular - and in many cases it can convert more of it, not less, to useable power. On an engine that does not require higher octane, in most cases it will have no detrimental effect to the vehicle, but no improvement either unless you get better gas mileage because your wallet is lighter.

Over the years I have owned numerous vehicles that got enough better mileage running on premium to MORE than make up for the difference in price. And this was in the days before electronic engine controls.