Originally Posted By: Jeff_in_VABch
Originally Posted By: NHHEMI
I am actually going to refrain from comment on it.
People can do what they want with their vehicles. I don't understand why you wouldn't follow the mfg's oil weight guidelines but to each his own.
I am recommending to follow the mfg guidelines, just for the 2500 truck using the exact same HEMI engine.
For heavy duty use such as in a 2500 truck, they recommend 5W30, better HTHS.
The HEMI is a gas guzzler. Some people would think (me included)that the 5W20 was for increased fuel economy. However, I have tracked the fuel economy on every tank of fuel run throught this HEMI (58K miles). There is no measureable difference in a 20 or 30W oil on fuel economy in summer usage. I have not used 30W in the winter. The 20W might produce an improvement over 30W fuel economy in winter.
One reason to run a 20W in the HEMI (in winter) is for cold start oil flow. The HEMI has a long initial start high idle cycle (1400 RPM for 30 seconds, varies) to light off the converters. It does this every time you start it (unless you have a programmer). In the winter on really cold days you would be asking for oil flow issues with a conventional 30W. I can see the mfg asking for a 20W for this reason alone.
IMO, the manufactures dont know jack about their current vehicles. They are broke and short staffed. They are in a struggle to survive, not a struggle to build an engineering masterpiece. They base decisions on attorney opinions and cost-benefit criteria. Their insurers and actuaries have a hand in the entire design process.
Look at the SVT and SRT vehicle owners manuals where engineers actually evaluated performance criteria and you can see engineering based decisions on oil and lots of other interesting items.
I am not talking oil weights for MPG reasons. I am talking oil weights due to mechanical requirements of MDS.
The 5.7L engines technically aren't "exactly the same" between the 1500's and 2500 & 3500 HD models though because from 06 on the 1500 Ram's with the 5.7L all have MDS whereas the HD trucks do not have MDS to contend with. Extra parts/different lifters in the 1500's w/ MDS vs those 5.7L's w/o MDS. The MDS system uses oil pressure to activate it so IMO you need to use the recommended oil which is 20 weight.
MDS is only available in 1500 Rams. Had I known you were talking HD trucks I would not have commented as I did. You can't recommend HD truck oil requirements for those with a 1500 and MDS though. Not unless MDS has been deactivated as I mentioned earlier.
Yes, for some Rams w/ 5.7L 5W-30 was the recommended weight...
03-04 = 5W-30( 10W-30 allowed for )All Models
05-06 = 5W-20 All Models
07+ = 5W-20 All 1500's w/ MDS & HD's under 14,000lbs GVWR
07+ = 5W-30 HD's over 14,000lbs GVWR
IMO if you have a 2006+ 1500 w/ MDS stay with a 20 weight. If I had a non MDS Ram w/ 5.7L, regardless of model, or I had MDS deactivated, I would run 5W-30.