Oil Consumption and periodic rough idle question for the experts

jbodenhamer · October 4, 2014

Thanks in advance for help and advice from folks here. I have searched the forum but found varying answers to my questions.

I have a 2012 Silverado Z71 crew cab 4x4 with the 5.3 aluminum block/heads and 6 speed auto. I just changed the oil today at 19,905 miles. I change every 5K at which time the oil life meter still says I have between 35 and 45% oil life remaining, but I do not like to go that long on oil. This was my 4th change, and I bought the truck new in Alabama in Oct 12. I now live near Detroit, MI (active duty Army so I move a lot).

Anyway, just like the last two changes, the oil was about 1.5 quarts low and pretty black today. Research on here about oil consumption has me wondering about that amount of usage. Exhaust pipe is pretty clean and I have never seen it blow smoke. I use a DEXOS approved oil for all changes (have used Valvoline or Mobile 1 Synthetic every time, which is what I put in today, and either Napa Gold or AC Delco filter-I installed an AC filter today). What are the opinions of this level of oil consumption on here? I rarely tow anything(only towed a couple time with it, and will tow another large UHAUL trailer when I move again in a year or so). Mostly I drive it to and from work which is about 12 miles each way. As is clear from mileage, I drive cars about 10K a year.

The other issue I have seen is that at stop lights, for the last 10K miles roughly, it will periodically have a rough idle moment and then return to stable. Never dies, just a noticeable shake in the cab and then back to normal. When this happens the RPM falls to right around 500.

Last question is that I also have the crappy wax goo on the frame that is coming off all over the place and there is lots of rust where this is missing thanks to a winter in Michigan now. It has more frame surface rust than my 2001 Dodge Ram 2500 Diesel had when I sold it to buy this truck, and that vehicle had 3 New York winters on it and about 175K(I got it used with about 90K and put another 80K on it in about 8 years of driving it). Any thoughts on this?

For the local Michiganders who might read this, do you have a dealer recommendation to take it to for questions about this? The nearest Chevy dealer to me is Buff Whelan, but I have never been there and know nothing about them. Is there a better one in the northern Metro Detroit area to address these issues? I was hoping to get 10 years and 100K trouble free miles from this truck. That is roughly the amount of time I like to keep trucks. However, here in MI, I can get employee pricing on Chrysler vehicles (just got wife the dreaded Minivan a couple weeks ago) and think I could ditch this truck and get a gasser ram for about the same payment I have now, but my favorite gasser trucks have always been Chevy/GM and the old 80s/90s ones were near bulletproof, so I had high hopes for this. Not crazy about Dodge gas trucks so the idea of trading is not terribly appealing even with a good deal. I have put in a bed liner, just installed a homelink door opener in the overhead console today, have a nice hard folding tonneau cover, full weathertech mats, and a few other things for my Chevy, all of which cost a couple thousand combined and would not come with a new truck, so that is another incentive to hopefully sort out any issues and keep this truck for another 8 years or so.

Thanks for the advice. I really appreciate it.

Jon

j-ten-ner · October 5, 2014

Your best bet regarding the oil consumption is to bring it to a dealer to start a consumption test and get the engine fixed.

I'm not sure what you mean with: "...When this happens the RPM falls to right around 500...".

My truck is idling at 500 rpm just fine. Is your idling speed higher than 500 rpm? That is not normal (I think).

Anyway rough idle can be caused by oil crusted spark plugs.

so long

j-ten-ner

ifixedit · October 5, 2014

First off, thank you for your service! This may be total myth, but even top engine builders for racing and other high performance use will generally recommend you NOT use synthetic oil right away on a new engine and to instead use conventional and then switch to syn after a few changes and the engine has had a chance to break in. Synthetic seems to be a bit too slippery at first which does not allow a proper break in and parts setting in with each other as they should. Again, could all be myth. I'm also one of those that changes oil at 500 miles on a new engine to be safe as there are small metal parts from the many machining processes floating around in your new engine. I also don't care what the oil life meter says and have ignored (and also don't trust) what to me is a totally useless feature since day one. I've never went any more than 4000 miles between changes and am now at 202,000 on my 03 HD1500 and it uses about a quart between my preferred changes of 3000 or so miles using conventional oil, pretty normal oil usage as expected. No matter how new or old your engine is, dirt and microscopic metal parts are floating around and making their way through the passeges and parts in your engine, all this has a tendency to contribute to wear and premature failure of componenets, the longer you wait between changes, the more of this that's going on. Dirt is dirt and dirty oil be it synthetic or conventional wears out engines. For having under 20k miles, your truck in my opinion on one hand is already using too miuch oil, but in reality not knowing how dirty your oil could actually be, if it's all highway miles, in town stop and go miles, half dirt and gravel road miles, or somewhere in-between, 1.5 quarts low in 5,000 miles is actually quite good as at that mileage the oil is very dirty and has lost much of it's original lubricating properties. Reasonable expectation between oil changes of around 3000-3500 miles for any engine is between a 1/2 to one quart usage. Before I run off to a dealer I'd test by backing off to say 3500 miles max on the next oil change and see how low it is at that point. If you're around a quart low or less (which I'd expect based on what you report @ 5000 miles) I'd say you are fine and there's absolutely nothing to worry about and just keep up the lower miles oil change routine. Honestly I'd also maybe consider ditching buying the expensive synthetic oil too! Remember my previous dirt is dirt comment. ;-) If it's oil consumption is more than a quart in 3000 miles I'd say I assume it's under warranty, find a dealer and let them work on it and figure it out, same goes for the rough idle if it continues.

Black4x4Z71 · October 5, 2014

Since the oil consumption is often traced back to this engine's AFM system, you may want to invest in the following Range AFM disabling Device; http://www.autoanything.com/performance-chips/range-active-fuel-management-disable-device

Since adding this to my truck my oil consumption between oil changes has dropped dramatically. By the way, I also run only Mobil One and change oil every 5k miles.

mymaggiebell · October 5, 2014

First off, thank you for your service! This may be total myth, but even top engine builders for racing and other high performance use will generally recommend you NOT use synthetic oil right away on a new engine and to instead use conventional and then switch to syn after a few changes and the engine has had a chance to break in. Synthetic seems to be a bit too slippery at first which does not allow a proper break in and parts setting in with each other as they should. Again, could all be myth. I'm also one of those that changes oil at 500 miles on a new engine to be safe as there are small metal parts from the many machining processes floating around in your new engine. I also don't care what the oil life meter says and have ignored (and also don't trust) what to me is a totally useless feature since day one. I've never went any more than 4000 miles between changes and am now at 202,000 on my 03 HD1500 and it uses about a quart between my preferred changes of 3000 or so miles using conventional oil, pretty normal oil usage as expected. No matter how new or old your engine is, dirt and microscopic metal parts are floating around and making their way through the passeges and parts in your engine, all this has a tendency to contribute to wear and premature failure of componenets, the longer you wait between changes, the more of this that's going on. Dirt is dirt and dirty oil be it synthetic or conventional wears out engines. For having under 20k miles, your truck in my opinion on one hand is already using too miuch oil, but in reality not knowing how dirty your oil could actually be, if it's all highway miles, in town stop and go miles, half dirt and gravel road miles, or somewhere in-between, 1.5 quarts low in 5,000 miles is actually quite good as at that mileage the oil is very dirty and has lost much of it's original lubricating properties. Reasonable expectation between oil changes of around 3000-3500 miles for any engine is between a 1/2 to one quart usage. Before I run off to a dealer I'd test by backing off to say 3500 miles max on the next oil change and see how low it is at that point. If you're around a quart low or less (which I'd expect based on what you report @ 5000 miles) I'd say you are fine and there's absolutely nothing to worry about and just keep up the lower miles oil change routine. Honestly I'd also maybe consider ditching buying the expensive synthetic oil too! Remember my previous dirt is dirt comment. ;-) If it's oil consumption is more than a quart in 3000 miles I'd say I assume it's under warranty, find a dealer and let them work on it and figure it out, same goes for the rough idle if it continues.

i work in maintenance, but i am sorry your views on oil are not great advice, based on myth or not, synthetic is better than dino, although there is nothing wrong with dino. synthetic is in every high end automobile from factory and i am pretty sure there is lots out there on the internet about synthetic. there is information on the gm algorithm and ironically its seems to be the only thing i can count on in these trucks, as it does vary 1500km's or so, which tells me its working. there are numerous posts out there on "are u doing your car justice or wasting money" again on the internet or magazines. in my line of work we discovered we were changing lubricants way before their life was up. with the oil life thingy on the computer of the truck, i am doing the oil at about what the general rule of thumb is for changing the oil with synthetic. if u read what the capabilities of the oil is, the oil is still not being used to its limit, but i would not want to push it that far. changing oil as often is a waste of money and if i were down a half quart and well within my warranty, i would be screaming bloody murder. if i were at the mileage u have on your vehicle then a little bit of oil usage would be expected. guys think they are earning a badge of honour by changing their oil at a 5000km (3500 miles) but while you are not hurting anything, you are not gaining either. fyi, friends 2013 bmw x5 recommended oil change is 15000 miles!!!!!

ifixedit · October 6, 2014

i work in maintenance, but i am sorry your views on oil are not great advice, based on myth or not, synthetic is better than dino, although there is nothing wrong with dino. synthetic is in every high end automobile from factory and i am pretty sure there is lots out there on the internet about synthetic. there is information on the gm algorithm and ironically its seems to be the only thing i can count on in these trucks, as it does vary 1500km's or so, which tells me its working. there are numerous posts out there on "are u doing your car justice or wasting money" again on the internet or magazines. in my line of work we discovered we were changing lubricants way before their life was up. with the oil life thingy on the computer of the truck, i am doing the oil at about what the general rule of thumb is for changing the oil with synthetic. if u read what the capabilities of the oil is, the oil is still not being used to its limit, but i would not want to push it that far. changing oil as often is a waste of money and if i were down a half quart and well within my warranty, i would be screaming bloody murder. if i were at the mileage u have on your vehicle then a little bit of oil usage would be expected. guys think they are earning a badge of honour by changing their oil at a 5000km (3500 miles) but while you are not hurting anything, you are not gaining either. fyi, friends 2013 bmw x5 recommended oil change is 15000 miles!!!!!

Sorry, but the syn deal is largely an old wives tale getting most that haven't done their homework to spend more thinking they are doing themselves a favor, so I gues we'll have to agree to disagree! As I said, dirt is dirt! Syn or Dino, when it's dirty, it's dirty. Take an equal amount of Syn or Dino, add the same amount of dirt and other various odds and ends floating around in your oil @ 5,000 miles and tell me which might be a better scenario to have in your engine? If you do your research there is one and one only reason Syn was developed and was found to be a benefit in the first place. It was developed by the Germans during WWII, they found it added horsepower to their aircraft engines and it was no more than a molectular re-arranging to make it more slippery, it's still oil and not some new alien additive you put in your engine. I recently read a Hot Rod Magazine article where they went from conventional to synthetic on a given engine / car, and the end result was about 10 HP using synthetic over conventional. The benefits are it does lubricate better when CLEAN, it may lubricate better by a bit over the long run as well, but mainly adds benefit if you change your oil every round (i.e. you are involved in drag racing).

Pretty tough to argue with 200,000+ miles on my 03 HD1500, including a 98 Yukon I still have that's been through two kids and has been to hell and back with 210,00 miles, both that receive a regular conventional oil change @ no more than 3500 miles and NONE have never seen the light of day of Synthetic, and neither has ever used more more than a quart between changes. ;-)

Otherwise, run what you feel you think is best and change your oil!

BlackZ71Silverado · October 6, 2014

Nothing wrong with using a full synthetic oil right out of the gate. Most high performance cars come from the factory with Mobil 1 synthetic to include the Corvette.

For what it's worth, our race car engines, (GM smalk block 358) run Royal Purple from the moment they hit the dyno from the builders engine stand. Not sure where you heard the synthetic should not be used right away line.

I know you may not agree, I know I don't, but GM is going to tell you that the amount of oil usage you report is normal. I believe their claim was somewhere in the area of 1qt. within 3,000miles is normal.

I change my oil according to the DIC and it's never low. My trucks have not used a single drop of oil since new BUT they are both tuned with AFM disabled since I got them home from the dealership.

Not sure about your idle troubles.

Sent from my iPhone 6

using Tapatalk

ifixedit · October 7, 2014

Sorry guys, didn't mean to turn this into some kind of disagreement and I think it mostly boils down to what you are comfortable with. Concerning the don't use Syn out of the gate. I've been a gearhead for years, have subscribed to Hot Rod for years and have read a few times from differnent engine builders in articles that they "prefer" to break in the engine with conventional oil although it does lack some of the additives it had back in the day, thus they add in the break in additives from Comp Cams as an example, then go to full Syn. By the way they speak highly of Royal Purple and was one they tested to gain around 10+ HP just by changing oil. When it comes to Syn from my experience it varies from one brand to another. I will agree overall that Syn does lubricate better and the time between changes "can" be longer, but I still don't buy it will any protect better when dirty, if it does the benefits are probably marginal at best. Much of the lesser oil comsumption comes from improved machining processes, tighter tollerances and improved oil be it syn or not over the past number of years. I remember the days of a car having 75K and it was considered "worn out" and junk, now they go 200-300K and still run good.

When jboenhammer first posted here he reported @ 5K his oil was "black" which tells me it is very dirty and is exactly why I don't trust any oil past about 4K as I've also seen some pretty dirty changes at that point myself and was glad I changed it when I did. If your're running up and down gravel roads in very dusty conditions vs. all highway miles I certainly would not trust I can run to 5+K without changing oil.

I'm also an off road dirtbike / snowmobile enthusiast and have tried the so called best $25 a quart 2-stroke synthetics in the past and in one case using supposedly the best in the business found I had stuck powervalves after only one season of running and found a completely gummed and carboned up mess that took me an hour of soaking and scraping to clean up, the next year changing to another brand and haven't had a problem or touched it in 4 years. Probably the best thing I learned here is take all the claims with a grain of salt.