88 K5 Blazer- What oil to use?

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Hello all. Been lurking around the forums for weeks now and have became obsessed with engine oil LOL. Ok, so I am coming up on my first oil change on my 1988 K5 Blazer, 350 TBI 80,145 miles.
I am unsure what type of oil to use, 10W30, 10W40, high mileage?
The engine was not properly maintained by previous owner, there is some sludge in the engine and the oil filler cap was black with sludge on it. Could I get some advice or suggestions about what oil to run in the Blazer for the summer? The weather is going to start to get warm in 2-3 months.

1. What kind of vehicle you have- 1988 K5 Blazer
2. What your owner's manual says -- not just viscosity, but certifications (look for acronyms like API SM, ILSAC GF-4, etc.) and change intervals as well- 10W30 Energy Conserving
3. Where you live- Massachusetts
4. How you drive (easy? hard? fast? slow?)- Usually take it slow, but sometimes for fun I push it
5. What your daily drive is like (short trips? long trips? city? highway?)- Take it out once or twice a weekend to give it a run. Short to medium trip length.
6. Whether your car has any known problems- I notice some blue smoke coming out of tailpipe when I start it up.

Thanks,
Nick
 
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Run a few fills of 15W-40 HDEO, and substitute 1 quart of oil for a quart of MMO. Do this for 2-3 fills in a row, and run them for 2-3k each.

That will help clean up the engine a lot.
 
15w-40 in the summer is fine in a 350. Besides, the MMO will thin it out some. You could use a 10w-30 HDEO if you want to go thinner.
 
Alright, well what is the 15W-40 going to do to the engine that the 10W30 won't?
 
Personally, I'd seek out a HDEO like Rotella 10-30. That give you the cleaning of a diesel oil in the viscosity you want without the MMO.

Otherwise some short intervals of any good conventional 10-30 will probably fix the sludge over time.
 
Originally Posted By: bepperb
Personally, I'd seek out a HDEO like Rotella 10-30. That give you the cleaning of a diesel oil in the viscosity you want without the MMO.

Otherwise some short intervals of any good conventional 10-30 will probably fix the sludge over time.


I think I will use High Mileage 10W30 and see what happens. Anyone have a recommendations for a brand? How about a filter?
 
I would use Rotella 5W-40 in that 5.7 and 5K OCI'S for the first couple of oil changes. Push-rod GM V8's seem to tolerate heavier oils.
 
If you want to go with the high mileage route nothing to worry about there use any brand you find on sale. Max-life is the best selling. But in the long run choice you make will give you the same results. As for filters I would go with a Napa Gold or even a supertech e-core. That motor should last a lot longer if your cooling and filtraton system is properly maintained.
 
Originally Posted By: addyguy
Run a few fills of 15W-40 HDEO, and substitute 1 quart of oil MMO for a quart of MMO oil. Do this for 2-3 fills in a row, and run them for 2-3k each.

That will help clean up the engine a lot.
 
Seems like most of the people like this Valvoline HM in synthetic blend. You could also use Pennzoil Dino HM oils or the SuperTech Dino HM oils.

I've seen the Pennzoil in heavy weights of 10W-30 and 10W-40 at Walmart along with the SuperTech Dino and Valvoline HM Synthetic blend oil. They also carry the MMO in quart bottles and sometimes gallons.

If your going to run the oil for short intervals then any low cost filter that your select would fit the bill. Get whatever is on sale or the cheapest price and make your decisions accordingly. Good luck and let us know how you make out.
 
Originally Posted By: OSDCrusher
Originally Posted By: bepperb
Personally, I'd seek out a HDEO like Rotella 10-30. That give you the cleaning of a diesel oil in the viscosity you want without the MMO.

Otherwise some short intervals of any good conventional 10-30 will probably fix the sludge over time.


I think I will use High Mileage 10W30 and see what happens. Anyone have a recommendations for a brand? How about a filter?


Maxlife.

Also, yeah 10W-30 OR 10W-40.. i think it said to use 10W-30 when new, most ppl with Chevys use that.

Some use 10W-40 some even use 20W-50 (!) but in reality, all three grades or thee first two might be ok.

MAKE SURE ITS A HIGH MILES OIL!!!

Hope this helps. (I have a Chevy and most people use 10W-30 in it. Same 8"Era" as your truck. has a carb)
 
Wow, thank you all for the very informative replies! It looks like I will be using MaxLife 10W0-40 with a supertech filter.
 
Originally Posted By: addyguy
Run a few fills of 15W-40 HDEO, and substitute 1 quart of oil for a quart of MMO. Do this for 2-3 fills in a row, and run them for 2-3k each.

That will help clean up the engine a lot.


+1 That should work well.
 
Id run rotella syn blend 10w-30 to try to clean up a bit. Then Id move to maxlife 10w-30 for a few ocis to see if it helps consumption. If not, Id likely move back to the rotella.
 
What would be better for the summer though, 10W-30 or 10W-40?
Is there any benefit(s) using the 10W-40 as opposed to what GM says to use, 10W-30?
 
With the large quantities of 350s around that have run or are running hundreds of thousands of miles on 5/10w-30 with no problems, I can't see a reason to use the 10w-40 unless you get it for cheap somewhere.
 
Originally Posted By: umungus1122
With the large quantities of 350s around that have run or are running hundreds of thousands of miles on 5/10w-30 with no problems, I can't see a reason to use the 10w-40 unless you get it for cheap somewhere.


Or if you're going to run the MMO, (20%), with the oil, the 10W-40 might help keep the oil from thinning out too much.
 
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