My friend has a 96 250 and I'm trying to convince him that putting higher octane like 93 into his truck will increase performance and miles per gallon to his truck but he won't believe me. I've filled my 98 250 with premium only and I feel that it has helped me get better MPG and I do notice a better response from the higher octane. So for all you experts out there tell him its true, thanks.

 

Unless his compression is higher than normal, or he has other expensive mods done to his engine, a higher octane is not needed. Higher octane fuels actually produce a cooler burn, and a slower burn (which is why they are used to fight predetonation), so I'm not too sure you're going to see an increase in performance with a truck engine. (Of course, if you don't take care of your engine and have a bunch of carbon in the cylinders, your compression might be raised due to the reduced area, thus the need for a higher octane fuel)

Hmm, see:
http://www.boyleworks.com/ta400/psp/Mythsgas1.html
"Octane number is resistance to detonation. Higher octane will increase power only if detonation is present."

http://www.howstuffworks.com/question90.htm

Best,

 

I figure it does burn and run a little better like 1% better, but not worth the 12% extra it costs

 

This turns out to be a great resource, and examination of fuels, also: http://www.hdart.com/hdrt/doesgasmatter.html

 

It will not increase performance in that truck. Higher octane than needed increasing performance is an old wives tail that has been handed down for decades. It might ever decrease performance. But I suspect the computer can detect the slower burning fuel.....Van

 

I used to run 93 octane in my 92 F150 with the 300I6 and I could tell a difference from 87, but not enough to make the cost worth it. After I got tired of paying so much, I dropped down to 91 octane and after the octane hangover, my truck has more power than it got from either of the other octanes (guess 91 is just perfect for my truck). Personally I won't run anything other than 91, and since its only like 1 cent more to a gallon than 87, it suits me just fine. Anyway, just my input.

 

Higher octane gasolines are capable of releasing more BTUs (energy), but (big but), the engine has to be set up to take advantage of them to make more power. What is said above about them being slower to burn is correct. This property allows the use of higher compression ratios / cylinder pressures and more ignition lead without pre-ignition (or ping or whatever you want to call it), which will allow a higher power output.

In an engine designed for 87 octane gasoline, you will generally get a cooler burn and less complete cobustion with higher-octane gasoline than with the 87 octane. Exception #1 would be on an engine with high miles on it where you may have some carbon deposits on the valves or chamber. In this case, these deposits hold heat and can cause pre-ignition. A higher-octane gasoline will reduce that tendency. Exception #2 is that most modern engines with knock sensors will retard the ignition timing if pre-ignition is detected, and this will produce less power. Higher octane gasoline in these engines may produce more power, but I doubt that anything more than one grade up (e.g., going from 87 to 89) will do much. Generally, these systems are to protect the engine if you have to use a lower grade or get a bad tank full.

Unless you can burn every last bit of that fuel, you're not getting the full benefit of it. Subjective evaluations really don't mean much. Try different gasolines with your truck on a Dynojet and see what the numbers say if this is a big concern to you.

Rollei
Engineer / SAE member

 

Concerning carbon deposits or buildup, there are several products that can be added to a tank of gas that will remove them. K44 (I think that's the name) will restore a rough engine to a smooth idle. I use it every 10,000 miles. I've also heard Marvel Mystery Oil (wonderful stuff) will do the same thing.

So there's no point in changing octanes to compensate for carbon buildup, just get rid of it.

Regards, Robert.

 

Agreed, Robert.

Getting rid of the carbon is the correct way. Using higher octane gasoline is the lazy way out, but it's what most people do. Chevron's Techron is a good one, too.

-Rollei

 

This is off the Ford service CD:

Rough idle, hesitation, poor throttle response, induction backfire and stalls during cold start/warm-up may be caused by the poor volatility of some high octane premium grade unleaded fuels (91 octane or higher ([R+M]/2). When compared to regular grade unleaded fuel (87 octane), high octane premium grade unleaded fuel may cause long crank time.

Use a regular grade unleaded fuel in all vehicles, except where a premium unleaded fuel is recommended in the Owner Guide. If lean air-fuel type symptoms are experienced, determine the grade and brand of fuel used and offer the following service tips.

- Advise those using a higher octane grade fuel to switch to a regular grade unleaded fuel. For those using a regular grade fuel, advise them to try another brand.

- Do not advise using a higher octane unleaded fuel than is recommended for that specific engine. Ford engines are designed to perform best using a high quality regular grade unleaded fuel.

- Advise using a higher octane unleaded fuel to avoid potentially damaging spark knock or ping, but do so only after mechanical repairs are ineffective.

NOTE:
All unleaded gasolines used should contain detergent additives that are advertised as having "keep clean" or "clean up" performance for both intake valves and fuel injectors.

 

There are some OEM ignition contol systems which keep advancing the ignition advance until detonation is detected and then they back it off a little. These systems can get a little better performance from higher octane fuels. I doubt if Ford trucks have this type of system. My F-350 460ci Fi engine certainly doesn't benefit from any higher octance than 87.

This type of control system is common in turboharged race car ignition systems to maximize power under all types of atmospheric conditions. That's the good news. The bad news is if the knock sensor goes south so does the motor rapidly as the detonation cracks/melts piston,rings etc.

 

I feel that just about any test or change can be felt or witnessed easier with a four cylinder car one is really familiar with. Over time and testing I have come up with the following - please feel free to offer input or critique as I am still not sure my observations (over about 30 of my 40+ vehicles - took me time to develop and test the theory) are correct:

Rollei expanded on what I know to be true, and with that I offer this tidbit... now many of you may not ever have to resort to this as you can afford trucks now - but in the past I have owned plenty of really crappy vehicles (end-of-their-life, but cheap to me).

To use some of them, and keep them from heating up too much, I would resort to using high-octane fuel in the very hot summer weeks. I witnessed, and still believe, that the overall temperature on the guages stayed lower (during use and at idle) with a high octane fuel as opposed to a low octane fuel. Granted, this could have had something to do with carbon build-up, but I am one to have always used Chevron Techron (ever since it first came out at $16 a bottle - remember that?), so that may not be the case. (by the by, the carbon cleaning chemical(s) in BG 44K are about three times more concentrated than in Chevron Techron, so you might want to think about occasionally doubling the Techron additive to a tank of gasoline)

Anyway, to keep a prone-to-overheat car running during the worst of the summer months, I have used 93 octane in an effort to reduce the build-up of heat. As this practice may induce less-complete burns, this is not a money saving measure in that regard, but it instead is a calculation that attempts to spend a little money on keeping a 140k+ mile vehicle running instead of purchasing a new one (or just having a radiator explode, engine overheat, etc.).

Over the years I have seen a lot of people get this backward, and they still seem to do so, when I hear that they use a higher octane in the winter to 'treat their car well'. Well, based on my observations with small cars that take forever to warm up - if they warm up at all - on 0 degree Fahrenheit days, one will develop that needed/desired heat faster with a low-octane fuel (again, this boosts my hot/cold burn theory and its effects on engine operating temperatures). This becomes more imperative as I have had some small cars that refused to heat up (in the trips I took them on) enough to release the thermostat and keep it open - and it is important as today's vehicle computers expect engines to run at a specified temperature. If an engine doesn't reach it, the computer doesn't take the car out a running-rich, choke mode. This, in turn, would seem to be a waste of fuel over a trip.

Anyways, this hijacking of the post that dsfdsfsdafds started, and probably doesn't agree with, seemed relevant, and I would value the input of the posters who seem to know their stuff about the truths about fuel.

Best,

 

octane was not indicated to tell the amount of energy in fuel (BTU's). i am an engineer and have seen the data on this sometimes high octane fuels actually have lower btu ratings. octane is actually just a measurement of how much compression is required to make a sample of fuel "ping" high octane fuels have some more complex molecules that ignite slower (later) and give a slower ignition (whoosh not bang in performance engines). sorry to be off the point but there is no more energy in high octane fuels.

 

Good info. As I dont have a manual, .. what is the recommended octane for the 2.9l engine (1988 Ranger). My 2.5l mx6 runs better w/92 octane (here in Canada) than 87. What should I use in my truck? I just bought it yesterday and havent had to tank up yet.

 

87