I bought a new Chrysler Aspen with the 5.7L a couple of days ago, andI don'tknow which grade of fuel to fill up the Aspen's tank, regular or premium?I asked a car salesman at the dealer but they said just fill it up with regular and do premium every three times you fill it, and another friend with a C5 vette (also a 5.7L) said to do premium fuel all the time to prevent engine knocking? So tell me which do you use and what would you recommend for the Aspen?

 

it will say in the owners manual on what type of fuel to use

 

Yea I forgot to say that the dealershipI bought it from didn't get owners manualsfor the lastfive Aspen's they sold. So that is why i'm asking.

 

get them to get on out of another aspen

 

I bought the last one the dealer had. You can't just answer my question?

 

if i had that info i would we dont have an aspen on the lot right now so i cant get my hands on a manual. I just saw in another post with a 5.7 hemi 300 they said the mfg rating of fuel was 89 so I would say mid grade in your aspen.

 

According to the manual you should use 89. You can go to http://www.chrysler.com/owners/manuals.html#, and download the owners manual, and keep it on the computer. Did the dealer order you one?

 

Yes the dealer did order one and apparently they are backorderedon all the Aspen manuals so I won’t get it for another month or so.

 

FWIW, I've used regular gas (2007 5.7) for decades and never had a knock even when pulling a loaded U-Haul through the Colorado mountains. I have also tested premium and my MPG was about the same - MPG gain not worth the higher fuel cost..