Turbo Dodge Forums banner

Fuel grade

3K views 29 replies 15 participants last post by  musqlar55 
#1 ·
Is premium fuel necessary in our td's, I know it wasn't in my other tubo car!!!
 
#2 ·
i run 93 in my turismo and my daytona as it makes it run a heck of a lot better than 89
 
#6 ·
I remember back in 86 I was delivering pizza with my 85 Shelby Charger (AH!, Memories), anyway. I got much better fuel economy running premium over the lesser grades. In fact it made up the difference in price to run the premium.
I also know that my 87 GLHS with a heap more power is doing even better than the 85 ever did for fuel economy.

Law
 
#8 ·
i only run premium or if i am broke i will run 89 but i can tell a differnce in fuel mileage, my sundance gets 24mpg with premium and with 87(long story) it will only get 17 to 18mpg, my mini doesnt care what it has lol dont know why but it gets 22 with all fuel grades. but i still run 89 or better, the only thing i run 87 in is my 90 2.5 dakota just becuse it get better with the cheap it will get 21mpg with 87 and the other grades do the same so not a big deal,
 
#9 ·
It is worth testing your fuel economy at each level, but with the 4 and 6 cylinder cars I have had, I have found premium fuel made a huge difference with regard to fuel economy, while the V8s showed no real difference. If you're just cruising around and not getting on it all of the time, the lower octane is probably fine, but run a tank or two of each and record the results to determine if it is worth spending a little more per tank at the pump. For me, it has paid off.
 
#10 ·
lol i only tested the fuel at differnt levels in my truck becuse i was driving 5 hours one way and i had nothing else to do! LOL :p and with my van i was curious becuse i ran 89 and it was good so i tryed 93 and it didnt change? :( my sundance my mom put a full tank of 87 in it! well it lasted 2 days of driving.. and was spark knocking alot while driving.:bang head
 
#12 ·
You aren't likely to do either, really. Depending upon where you drive, you will have higher or lower octane for premium anyway, so if you were to drive across the country, you may come to a point where premium is 90 octane. If you're driving the car hard, the higher octane will help performance, but if you're just cruising, you may find the lower to work.

Either way, for my driving, I found my two Daytonas both get better fuel economy with 93 vs 87 or 89.
 
#15 ·
I have never tried mixing fuel grades to see if it would be worth the hassle, but I have known people who have mixed them for one reason or another. As for mods, sure they can have impact. I actually saw a 6 mpg improvement after extensive mods on my TII Daytona. It would depend upon what was done and if it was done correctly.
 
#16 ·
Again, back with my 85 and delivering pizzas, I did mix 1/2 and 1/2 between 87 and 92 Octane with the equivalent power and slightly better mileage than either grade alone. That might just have been in my teen-age brain tho. I only did it for 3 tanks because I thought it was a pain to do and I was rolling in pizza tips...LOL

Best places to start looking for improved fuel efficiency is
1) Clean air filter
2) Cleaned and properly gapped plugs (hotter too maybe?)
3) check that timing is bang-on

I may just be talking through my hat though. I'm sure there are lots of other guys with more/better info that would be willing to help you.
mpgmike is a good source of information and he has lots of experience working on the Xprize stuff.

Good luck
Law
 
#18 ·
I thought the octane rating was simply a resistance ratiing. Meaning it resists detonation.
Depending the needs of your engine ie: compression ratio, determines the octane rating used.

It has been tested many times over the years, mostly in the racing crowd, using higher octane gas when not needed actually produces less power. (because of the higher resistance).
I don't know about increasing or decreasing mileage, that was not the purpose of all the tests I have seen, so I won't get into that dabate.

Pump gas, as mentioned, is not reliable on the ratings. Probably why there are different results for some of you guys.
 
#23 ·
As far as mixing I Meant I have half a tank of 93 now and try and fill up on a lower octane!
I was told that e85 is not a good idea due to not good on fuel parts as its not designed for that!!
I don't have access to race gas!
As far as compression ratios I am certain that th po didn't do anything to change that, so what ever stock is!! And what else besides piston change and things like that will change compression??
 
#24 ·
my dad had to mix fuel in his 84 suburban. we put a low mile 406sbc (bored 400) in it back in the mid 90's for trailer towing. the engine ran awesome on 87 driving solo but the tuning was just "hot" enough that it would ping slightly while towing. with the range of a 40 gallon tank it was easy to swap back and forth between 87 and 89 every time we got down to 1/2 a tank. worked like a charm on a month long cruise from maine to yellowstone and back with a 6,000 pound camper behind us.
 
#25 ·
well i was stupid and put like 9 gallons of e85 and i can notice a bit more hp but it misses/stumbles when i start to get into the gas....never do that again til i can get a cal for e85 and bigger injectors...

now i just gotta run that e85 out or at least down to 1/2 tank and get to premium again..

how much damage have or will i do without the cal or bigger injectors until i run this e85 out????

and a side note i heard the +20 inj were only good to about 20 psi... and told to get 90 talon or eclipse ones as they can get higher psi...is this true >>>??? thanx
 
#26 ·
I've run 87 on a stock T2 and with boost pushed up to 14 psi (G-valve) and didn't do any harm, but the I could feel the computer retarding the timing and the resulting lack of power. On my later T1s that are all stock and push no more than 10 psi I use 91. 93 seems to have no improved performance and with 89 sometimes it feels like the power is a bit off, sometimes it's fine, probably other factors like temp, humidity, gas quality ect at play. Around here only Sunoco carries 91, everwhere else it's 89 or 92/93. Now on that T2 I mentioned at first, after going with +20s and a cal for 18/19 psi I only use 93.

One thing I don't see getting enough attention is driving conditions/style. For me here, "around town" = you can't go more than 4 or 5 blocks without hitting either a stop sign or a red light. For other people "around town" could mean going 4 or 5 miles at 40 -50 MPH without hitting a traffic control device. That makes a BIG difference.
 
#28 ·
One thing I don't see getting enough attention is driving conditions/style. For me here, "around town" = you can't go more than 4 or 5 blocks without hitting either a stop sign or a red light. For other people "around town" could mean going 4 or 5 miles at 40 -50 MPH without hitting a traffic control device. That makes a BIG difference.
I agree, it's all relative.
 
#29 ·
I have a car that had extremely high compression due to some schmuck selling me the wrong pistons in my engine kit. I ended up changing the pistons, but before I did, I was mixing E85 with regular gas to up the octane rating of the fuel. It does work, but you don't need as much as you used. I was using 3 gallons of E85 in a 15 gallon fill up. This engine had over 12-1 compression (long story, but the pistons were for the wrong year). The pinging was gone with the mix, but it pinged like crazy when I didn't mix the E85 in. It is not the best solution, but it does work. In your case, a gallon or two of E85 in a tank of 87 octane would work.

Also, the standard R+M/2 octane formula does not really show the true advantage of the E85 as far as eliminating detonation. Alcohol is a very slow burning fuel compared to gasoline. A typical race engine built to run on alcohol can be in the 14-16:1 compression ratio area and not have detonation problems. It is also usually required to run an extra 2-4 degrees of timing, but again in your case, if you're just looking for resistance to detonation, then add a gallon or two per tank and call it good.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top