Has anyone run 90 octane pure gas (non-ethanol) in their 2004 D2. Curious if that fuel would run better in our trucks. I currently run 93 (10% ethanol) and was considering a change to improve performance.

 

The internet seems to claim "Ethanol is similar in acceleration, power, and cruising ability, but ethanol miles per gallon are less than pure gasoline."

Basically run it and see, it obviously won't hurt. Many people run Regular gas in vehicles that the manufacturer reccomends Permium gas for best efficiency(EPA numbers).

 

Since the GEMS/Bosch Motronic systems have knock sensors yep I run 87, 91, but mainly 87 octane. In my 95 D1's I run 87 with an octane booster.

 

What Best said ^^^^. Once it dawned on me that D2s have knock sensors which afford the ECU the ability to retard the spark and prevent detonation, unlike my other cars, I switched to 87 Octane in all my D2s and haven't looked back. I have noticed zero difference on all fronts. There may be more carbon buildup inside the engine if you believe the oil company's claims that higher octane fuels come with more/better detergents to "drive your engine clean", but economy (or lack of) is the same and there is no noticeable loss of power in daily driving. The only difference that the change made was to my company's bottom line, since they pay for my fuel. I do it because I don't believe in wasting money, not because it's specifically saving me any. The oil companies make plenty of money already.

Two points of clarification:
When towing I run high-octane fuel because the engine will develop more power with the timing changes that the ECU will be able to implement.
Non-ethanol fuel is important for vehicles that sit for long periods of time. The ethanol will break down and gum up the fuel system over time, otherwise I don't see why it would be important for normal driving.

 

Thank you everyone for your feedback. I'll try some 90 or 91 pure gas this week and report back on my findings.

 

I am surprised by folks who do not notice a difference between 87, 91, and 93 octane in our rigs. Maybe it's a geographical (ie. atmospheric) difference, but I have noticed very noteworthy differences in economy, power, and how smooth the engine runs even between 91 and 93 in my area which is mostly between 1500 and 2500ft elevation. So has my buddy with a D2 who ran 91 for years and was very surprised when he switched to 93 for a couple of tanks. He won't go back now because he made up the cost per gallon difference in increased fuel economy.

As for the difference between ethanol and no-ethanol, there are certainly benefits to running no-ethanol. Fuel lasts longer, doesn't collect as much moisture, and is a bit more "energy dense". Ethanol/Alcohol also has a different stoichometric burn ratio, and requires a richer fuel/air mixture for an optimal burn meaning there is a slight difference in fuel economy. At 10% ethanol that fuel economy difference is not a lot; generally 3-5%. As far as differences in octane rating, that indicates a fuel's resistance to ignition. A 90/91 octane fuel (for example) should require the same energy to ignite whether it it 85% ethanol, 10% ethanol, or pure gasoline.

 

Where I live & drive = no mountains, so 87 works fine. When I've traveled to a region with mountains I found the difference in 87 & 91 octane was like 5-7 cents difference so yep I switched to the higher octane while I was finding it for that little price difference however in my neck of the woods 87 to 93 octane is more than a 1.00 difference per gallon!!! Sorry not gonna use that when I can buy a decent Lucas Octane Octane Booster for 8.00. I drive my LR V8's hard, I let em rev all the way up vs drive like mrs daisy and carbon has not been an issue. I've also towed a D2 with a D2 several times with 87 & 93 and it did the job exactly the same. Funny thing is if I travel just 4.0hr away to Austin 93 is maybe .25 more, but in my area it's pure savage $$$$'s for it at the pump.

 

do it.

i notice a difference in both my '04 Discovery and my 2000 P38 when i run 91 or 93 pure gasoline vs 93 10% ethanol fuel. better MPGs and better (seat of the pants for sure) power. Missouri doesn't have any pure gasoline stations that i know of, so i am only able to get it when i'm in Tulsa, OK.

 

Perhaps it's that I don't consider these engines to be especially powerful, and that the trucks weigh almost a full ton more than my cars which do have high output engines in them, that I never really pay attention to the power they "aren't making" when I drive the Discos on regular fuel. They always feel pretty slow to me. For the reason I already mentioned about the ECU's ability to run more spark advance when there's no detonation present, it makes total sense that high octane fuel should generate more power to the wheels, we're in agreement there for sure. However, if you want to assume that there's a 10% reduction in power by using 87 (which is probably way too high), the 4.6 still makes more power than the 4.2 will on 93. I just don't notice a swing of 10 or 15 HP in a vehicle that takes about 10 seconds to get to 60mph anyway. Throw larger tires or other off-road mods on there and that number goes up further.

So, I believe you guys are feeling more power in the butt-dyno (and even a real dyno should show it) when running high octane fuel, but in my opinion unless you're in a high stress environment it really doesn't matter. I find the difference truly imperceptible.

 

I've ran em on both and you'd feel more pep in your step adding 5psi to the tires. V8 isn't known as a rocket, but vs my 05 Jeep Wrangler I6 4.0's at least I can get up to 80MPH!!! Dang I6 4.0L was done at 65MPH with the automatic....

I always reset my adaptions at each oil change on both my GEMS/Bosch setups and then drive em pretty hard until it learns how I drive. I'll toss an octane booster in the 14CUX setup's for sure, but D2's eh not as important.