I didn't get a manual with my Dodge Ram when I purchased it used but I was wondering what type of gasoline should the5.9L V8 engine be running on?Would one type make it run better, or that just talk?

 

Everyone has their own opinions, and one truck will be different from another, but i've always used 87 in mine.(85 now that i'm up her in CO), and have been getting a steady 13 in the city...not sure since the lift, but stock you should get somewhere around there. If you don't have exhaust or CAI you may get closer to 10 (at least this is true in my case). You will not see any better mileage with higher octane unless you are driving a vehicle made to specifically run on it..(SVT, Supercharged f-150s....etc.) Most fuels have different addatives and detergents so you can get a cleaner fuel from certain stations. I personally have always got it at shell and will never buy gas from 7-Eleven!! I'd say go with whatever you can afford!

 

I agree with 94Ram4x4 the manufacturer's design these engines to perform at an "avg" fuel grade with the higher octane needs going to the suped up vehicles. Could you run a 93 octane, sure but unless you have a high hot spark ignition you will not fully combust all of the fuel thus creating a higher carbon buildup on the plugs, and combustion components than if you used a fuel that totally combusted during the spark cycle. Now there are many different opinions regarding this subject I'm sure but I only run what the truck designers recommend and I get 13mpg hwy with a 6" lift 5.9L V8 etc...(see sig at bottom) running 70mph. The only additive I use is Lucas in each full tank. Also like 94Ram stated stay away from these cheeseball gas stations you don't know what you are getting there. Hopefully this helps.

 

Stock engines were designed and tuned to run on 87 octane. They run fine on it unless there is some other problem present. Running higher octane may mask the problem but won't fix it.

 

Higher octane is usually called for in higher compression motors. The higher the compression ratioof a motor the more the tendancy to detonate. If your motor is stock andhealthy,you should be running at ~9:1 and should be fine with 87. This is unless you have done anything to alter the stock fuel/timing maps in the pcm.

 

Good reading on octane ... when you're bored or curious:

http://www.prime-mover.org/Engines/G...es/octane.html
http://www.offroaders.com/tech/octane.htm
http://theserviceadvisor.com/octane.htm
http://retail.petro-canada.ca/en/independent/2069.aspx

 

stock pcm timing and leaky plenum i ran 87 ok.
hypertech and leaky plenum required 89-91 to avoid pinging.
hypertech and fixed plenum will run 87 again w/o ping.
i don't think my mpg changes with different octane. its a steady 13 city, 15 hwy.

 

Are you saying that you ran the 93 Hypertech program on 87?

 

no. i set hyptech for 87 octane, ran 87 and got pinging due to plenum. temporary fix was to run 91-93 octane gas. i have not yet tried hypertech set for 93 octane, and probably won't. the gas is too expensive.

 

Yeah, the last thing I really wanna do right now is pay more for gas when my baby is already a gas hog. It'd be different paying a bit more for diesel