I have a couple of questions. I have 2005 5.7 Ram Hemi with 28k. I took my truck to the dealer because of the check engine light and was told it was the catalytic converter had gone bad. Thiswill be my second replacement since I got the truck brand new. Has anyone had this problem or can give me some info. My second question is what is the best gradeof gas to use with Hemi motor? (I dont use 87)

 

i believe the manual will say 89... thats what mine says and thats what i use....

 

I really think you need the dealer check out as to why your two cats failed. I would look into your egr valve,o2 sensors, etc. I would be guessing its the egr valve since that is a common part that often gets replaced on the hemi

 

thanks 287c i will check with dealer about that.

thanks for the info tdmopar59, also have you heard or know a higher grade gas given better performanceand burning slower for better mpg.

 

not without a tuner... higher octane is a higher price and thats all unless you get a tuner for your truck than you will get the performance aspect...

 

Yea, if you've killed two cats now, you have other issues going on. A stock cat should last well beyond 100,000 miles. I wouldn't let it leave the dealership without them checking everything, starting with the EGR and working back.

Studies have shown that without a tuner you get no benefitsfrom using any grade of gas above 89. Stick with the 89 octane and save yourself that 10 cents a gallon. Now with a tuner, your timing will be advanced (among other things) and that alone would require a higher octane fuel.