oil change

[flattire]

hey how often should a guy change oil im using rottella 5/40 synthetic

[trukdoc]

...really using 5w40,instead of 15w40...you need to change it NOW...6.5s are factory recommended for 15w40...any lighter oil will NOT retain proper viscosity for lubrication purposes...this is a turbo engine...it neeeeeds the proper viscocity oil for turbo survival...

[flattire]

i don't want to sound ignorant but ur in texas warmer than our minus 40 deg winters do u honestly think my truck would start after sitting all nite at that temp. lots of guys use even 0/40 synth. up here in the winter but thanks for the answer.

[JD_countryboy]

could you fill in your loaction in your signature? The fact you noticed it in truckdocs post made it easy for you to ask a more specific question. Yes engine is designed for 15w-40. In such sub zero temps, do you take measures to help truck start easyier? block heater, garage kept, oil heater? Just cause its cold outside, just means it takes oil a bit longer to warm up. Cold will affect flow properties just as heat will.

[trukdoc]

...you got me curious,so I looked...according to ALLDATA your truk should use CG-4 in a 15w40...so as long as your oil is CG4 you should be all right,however the people that designed that engine don't care where it lives...up north of I-20 with you snowbirds or in a hummer in persia...the recommended oil weight is still as they say preferred...a viscosity chart in an owners manual might give you a choice for xtreme temps,but it still WON'T go below the equivalent of 10w40...jd

[flattire]

thanks for the info guys i do park in the garage in the winter and use my block heater outside when i have power avab. but that dosen't always happen when i bought the truck i used shell 15/40 all the time till i started havin problems in the cold then went to mobil 0/40 was good 4 starting but used oilmy motor doctor told me if i stayed with synthetic to use shell 5/40 i did now i use very little oil. guess its back to 15/40 till i can find a solution to winter temps. what is cg4?
thanks again

[grancito]

CG4 is oil quality specification, it is printed in a circle on the oil container.

[God prefers Diesels]

Problem is, if you want to use synthetic you're stuck with 5/40. Rotella, Prm Blue Extreme, and even Amsoil are 5/40. The Royal Purple diesel oil I had in my 6.5L was 5/40, but now they make a 15/40. Course, my truck blew up with 5/40 in it...:rolleyes:

[ZiGBlazer]

I switched my 6.5L to rotella synthetic 5w-40 last year. Before the coldest I could get it to start without being plugged in was 6 degrees. This winter it started at -16 degrees without a problem with the synthetic. There is a big difference in the cold viscosity between 5w-40 and 15w-40 and almost no difference in warm viscosity. The Amsoil 5w-40 actually is thicker than standard 15w-40 at 212 degrees and has a much lower pour point.

In other words in cold climates your engine will have much better lubrication on startup using a 5w-40 over 15w-40. Synthetic really helps but not as much as the 5w-40. When it gets below zero it can take up to 2-3 minutes of running for conventional 15w-40 to reach the rockers in the 6.5L. It also is too thick on startup to flow through the oil filter, opening up the bypass to let unfiltered oil to be pumped through the engine. That is one of the biggest arguments for synthetic oils in colder climates.

Over the road trucks (semi's) don't have the problem as much because they have much bigger passage ways and much larger filters, as well as much larger oil pumps. 15w-40 flows easier in large diesels than in our small diesels that are more like a small block 350 than a 12 liter mack. You may have pressure in 10 second, but hardly any flow to the cam, lifters, rockers, and rod bearings.

[flattire]

well thanks again guys i checked mobil and shell here in alberta and they both said not to worry their 5/40 syn. is gold and i will not have any problems but i will shorten the mileage on oil changes and maybe even change filters half way through thanks again 4 the info

[vmac4]

to answer your original question.the recommended oil change interval,is 3000 miles.Now there are a lot of people extending there intervals because they run synthetic.I would do an oil analysis before extending the oil change interval.Like everyone has said that the 5w40 is not the manufacturer recommended oil,extended oil change intervals are also not recommended.
A couple of oil sample tests,and you will have a good indicator of how your oil is performing and the recommended oil change interval.I would still change the filter every 3000 miles(if you extend the oil changes.)