New LS owner...oil questions..Dexos 1...

[bandit0067]

Not sure if posted in correct forum , Mods move if needed. Guys, just bought my first truck/LS engine, a 2013 Tahoe. Owners manual says, 5w 30w only , NOT 10w 30w, why is this? I understand 10w is a bit more thicker and mileage may be less, but I have never seen it written that strong not to use. Is it a big problem to ALL LS engines or just the year[s} I have.

I trying so read up on this recommended Dexos 1, what is it , a new additive. What EXACTLY does it do for the engine that the manual says NOT using will void warranty. My truck is used so warranty is not a factor but do wish to prolong engine as best as possible. Do all LS engines need this Dexos 1 or just my year[s]. Is this Dexos just a way to put money in GMs pocket come oil change time in their millions of engines.....thanks for your opinions....

[Palf70Step]

Dexos is just their synthetic blend. As long as you are using a compatible full synthetic you should not have any issues. As far as 5W-30W vs 10W-30W, the 5w is better for first start/cold starts. The weight isn't always about thickness (heavy) of the oil, but its flow characteristics. I try to run 5w-30 on my DD, but being I am living on the surface of the sun in southern mississippi, I don't see, nor have seen issues with the weight difference. I do try and keep the 5w in it during the cooler (relative) winter months.

[bandit0067]

Thanks Palf, I was thinking there was some additive or special formula in Dexos 1 that those engines operated better with. But its just GMs brand of synthetic oil. Well , you will not get that from the owners manual....they scare you pretty big into thinking big problems if one uses another weight or brand in this engine. PO of the truck used independent oil/service businesses and did not know what they used, syn or non syn.

[Palf70Step]

My wife's Honda is the only full synthetic I have and we use Mobil 1 on it cause the dealer did. Depending on the price, most full synthetics are about same price from what I have seen. I know each company has there so called magic formula, so with that if the cost is about the same I might go along with the Dexos thing, if not I would go with Mobil 1 or Castrol's full synthetic.

[1976gmc20]

All I know is that I bought some compatible store brand oil at O'Reilly's just to carry along on the road. Haven't had the oil changed yet but I'm sure I will have it done at the tire shop where we get our other vehicles serviced.

[Bob B.]

Dexos is not an additive, it is a set of oil specifications that an oil must meet to be approved for use in late model GM gasoline engines. Came out around 2011. A Dexos approved oil may be semi- or full synthetic, and many premium motor oils meet Dexos specifications. Mobil 1 5W-30 is a Dexos approved motor oil. So is O'Reilly's 'house brand' 5W-30 full synthetic.

[bandit0067]

Thanks Bob B. So, if one had Mobil 1 bottled before around 2011 , it would prolly not be made to that specification , correct. But that was not something that affected LS engines made from 2000 to 2011. Wonder what was changed in the engine internals that needed the new specs or by years of analysis it was determined there was a problem.
Was heading out on long trip and did use older Mobil 1 for the trip. I shall go purchase the newer Dexos speced oil....thanks much

[MJN]

API standards have changed and there is even now a GM Dexos1 Gen 2 specification and are backwards compatible. Typically changes are made for the additive packages and detergents in the oil to prevent breakdown and volatility at the higher temps these new engines run at and especially added stresses of turbo charged engines and direct injection engines. Don't be concerned about using 5w30, remember with a multi-grade oil it will perform as a lower viscosity oil (5 weight) below 32 degrees and a 30 weight at warmer temps. Usually tighter tolerances require a lower viscosity oil so it flows easier into tighter areas, it will take less time for a 5 weight to get to critical areas than a 10 weight. Emissions also plays a key into this and the engine doesn't have to work as hard to pump the lower viscosity oil and will use less fuel. There are some import engines that require 0w16 oil now, 0w12 and 0w8 are even expected to follow.

[jocko]

Bringing this one back to the top for a follow-on question. Like the OP, I've now entered the era of Dexos recommendations.. My 2017 6.0 says you can use synth or synth blend 5W30 as long as it meets Dexos 1 Gen 2 specs. It was mentioned above that Dexos spec can apply to eithe full synthetic or synthic blend. I begrudgingly transitioned from conventional 10W30 (in my older trucks) to synthetic blend because I couldn't find much conventional oil locally. In regard to this truck, I've yet to find a Dexos 1 Gen 2 spec compliant synthetic blend, only full synthetic. The full synthetic is pricey, and I get it, it lasts longer... but iI have a few questions

1) first of all - has anyone found a synthetic blend Dexos 1 Gen 2 compliant 5W30 oil?

2) for those that use full synthetic, what oil change interval do you follow? Or, do you just let the GM oil life system tell you when to change your oil?

3) Nowhere in the owners manual does it state the oil change interval (that I can find), it only says that "IF" you for get to reset your oil life monitor at an oil change to then assume the worst and change your oil 3000 miles later (the interval I normally use on all my vehicles, but that was not with full synthetic oil, have never used it before). Sorry - here are the questions I'm getting at -

a) what (or approximately what) oil change interval does GM use in the oil life monitoring system? (I realize their calculation is not just miles-based, but composition based also - but curious
how relevant/accurate/conservative/not-conservative the oil life monitoring system is)

b) does anyone know if the oil life monitoring system "assumes" you are using a full synthetic oil? If so, why does the owner's manual direct a 3000 mi interval if you forgot to reset your oil life monitoring system?

Thanks for your time. I probably just need to drink the kool-aid and come into the 90's and use full synthetic and see how many miles the oil life monitoring system gives me on average per oil change... Just curious your all's experience. This is my first vehicle newer than a 2001