First Post.
I just bought a 09 Ram with the Hemi 5.7 liter engine. It's the first Dodge I have ever owned. I know zero about engines. I have under 800 miles on it.
When I bought it, I asked the dealer about the octane rating requirement. They (salesman) told me it uses regular gas. Then I find out in the manual, 89 octane is preferable. When I questioned them on this at my free car wash, they said 87 acceptable, 89 recommended. I have been using 87 octane (pure gas) no ethanol. Truck seems to run fine, but I plan to use 89 from now on. Any knowledgeable opinions are appreciated.

Since I use only pure gas, I use Costco. They have only 87 (regular) or Premium. Is there a safe way to mix/formulate these two grades to achieve 89 octane. The manual says NO premium fuel.

Thanks
John Valdes

 

It says no premium? I just put 93 in my truck today lol

 

If it run's fine on 87, which mine does, then why consider changing? I'll stick with the 87 until someone can show me where an increase in mpg will offset the increased cost.

 

it's not that you shouldn't use premium it's just that it's a waste of your money.

Basically the engine is tuned to properly perform at it's highest using an 89 octane fuel. Running an 87 is still ok, but it will be at the cost of alittle horsepower, fuel mileage, etc.
Running 93 will also still work, but in this case, the engine is not running enough compression or whatever to fully utilize and ignite all of the fuel when running 93. It may be the case where the 93 has a few more additives and such that could bring some benefit, but few people realize that unless your car is tuned to run on premium that they're just letting money run out their tailpipe in wasted fuel when using higher grade gas than the engine is made for.

I'm sure someone here has alittle more technical explanation, but this is my understanding of it, so i'd say use the 87, but if for whatever reason you feel bad, you're welcome to use the 93, it's just a waste.

 

There will be no difference in mpg between 87 and 89. The only difference will be that you'll have slightly more power at WOT with 89 over 87. The engine is configured to prevent pinging, so it will not damage your truck running 87. You'll most likely never notice a difference unless you floor it all of the time or are towing a lot. Also, there are no additional additives in 89 over 87. 93 gasoline from a brand name (Shell, Chevron, or Texaco) on the other hand has additives which will help prolong the life of your truck. 93 from Costco does not necessarily have those additives and for the additives to truly work, you have to stick to the same brand of gas for at least 6 - 12 months. If you filled up with Shell, then Chevron, then Shell and kept flopping around like that then the additives from one gasoline would basically attack the additives from the other and you'd never see any benefit.

 

Just use 87.

 

The PCM will adjust for lesser octane gas and it will run just fine. 89 is better for peak performance, but not required.

 

Thanks for the feedback. I plan to use 89 octane ethanol free. Should I be concerned when I am on the road and pure gas may not be available. The manual is somewhat vague regarding blended gasolines. I will check mileage when I start on the 89 (next fill up) and see if there is any difference. I am getting 14.7 in town now according to the truck computer readout. How accurate is this built in function? The "Average Miles per Gallon" screen.

 

I use ethanol blends, there is nothing else for 89 in Iowa. My truck runs fine.

 

The blends which are mostly gasoline should be fine for all vehicles to run.

The blends which are mostly ethanol are definitely not safe for your truck.