CNG 2012 GMC Sierra Denali recommended oil

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morgancole

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Hello,

I've got a 2012 GMC Sierra Denali that I've had converted to run on CNG (can switch back to gasoline too), and I'm wondering what oil and filter people would recommend. It has 15,000 miles and the oil change light just came on, so it's time for its second oil change now. I drive about 3,000-3,500 miles per month, mostly highway. I don't have a lead foot but I drive harder than some. I installed a Volant air intake with the nicer air filter option, it's supposed to be a higher quality filter. Also I live in Houston, TX, so cold isn't much of an issue but it gets plenty hot.

I intend to drive this truck for quite a while and would like to run a good oil, but I don't want to waste money on oil change more often than necessary or on synthetic oil if conventional is just as good.

People seem to think that the CNG will extend the life of the oil because it doesn't get contaminated as much, but it seems it would still break down just as quick. Just to get the conversation started, I'm considering going with Mobil 1 synthetic and the Mobil 1 filter, and going 2x the regular recommended interval, meaning I would reset the light once and then change oil next time it comes on, which would be about 15,000 miles.

Any suggestions and advice is greatly appreciated. Thank you in advance.
 
Anything that is dexos1 approved should be just fine. These will mostly be full synthetic, but there are a few syn blends that are also dexos1 approved.
 
I would use a Dexos1 and just change it when it says to. If you wana start doubling your interval, get something that is designed for an extended performance application. Amsoil Signature Series and a Bosch Distance Plus oil filter could handle your 15k oil changes easily. If your more eco-minded try Mobil 1 Extended Performance or Pennzoil Ultra (if you can find it still). Both SHOULD handle 15k.

CNG people are correct in some aspects. But since you do a ton of highway driving, fuel dilution wont be a problem therefore the oil will breakdown at the same rate.
 
Originally Posted By: morgancole
People seem to think that the CNG will extend the life of the oil because it doesn't get contaminated as much, but it seems it would still break down just as quick.

Generally speaking, such a fuel will allow you to extend your OCIs because fuel dilution isn't an issue. "Breaking down" and other oil related issues depend much on driving style. People who choose CNG or LPG often do so because they're doing a lot of driving, and if that's the case, the oil is always at temperatures and there are no cold starts, so that also extends the life of the oil.

At least while under warranty, I'd recommend following the manufacturer's recommendations (i.e. the OLM and the appropriate dexos1 oil). Later on down the road, you could look at extending OCIs.

In our taxi service in the late 1970s to early 1990s, we were on LPG and used 6,000 mile OCIs on QS conventional, with Wix filters. The engines ran forever and a day and stayed clean, and the LPG certainly contributed to that. No fuel dilution is a nice thing.
wink.gif
 
If under warranty then change the oil as per warranty requirements. LPG doesn't contaminate the oil like gasoline does so the oil will last a bit longer in service but the only way to know for sure is to get a series of uoa done to establish trends and decide from the acquired data.
 
I will be the naysayer here and say be very careful in running extended OCI. I have had plenty of expereince running propane vehicles. Similar family of gas as NG. The oil never looks dirty but tends to get beat up quicker than gasoline. The valve area runs super hot and a common failure is burned valves. There is a reason the manufacturers beef up the valves and valve seats on NG vehicles. My input would be to use a "conventional" Dexos-1 rated oil, halve the OCIs and let the oil analysis determine the running rate OCI.
 
If you are going to extend OCIs, at least do a few UOAs to prove that the oil and engine can handle it. Otherwise you're just relying on fairies and unicorn dust.
 
Originally Posted By: NateDN10
If you are going to extend OCIs, at least do a few UOAs to prove that the oil and engine can handle it. Otherwise you're just relying on fairies and unicorn dust.


We all know what happens when you rely on fairies and unicorn dust.
lol.gif



Just curious: how easily accessible is CNG? As in how far do you need to travel in order to fill up? How does the mileage compare to gasoline?
 
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