Oil Change Question

Jkb242

Original poster
Member
May 19, 2019
239
CLT
I have an unopened 5 Qt. 10-30 full synthetic container I like to use in my daughter’s 4.2L it will likely need 6Qts but the only 1Qt bottles I have are 5-30 also fully synthetic. I’d like to use this combination on the next oil change due shortly and wondered if there is any input strongly against this one time mix. The engine is in super condition runs great, no leaks, and uses 0 oil between changes. I always used full synthetic oil and changed at computer suggested intervals. 120k miles.
Thanks in advance for input.
 

Mike534x

Member
Apr 9, 2012
894
There would be no problem with mixing the two of them, I've done it on my 5.3 without any issues and in the past with my other 4.2's. Does the line read full when you put in 6 QTs? GM calls for 7.
 

Mektek

Member
May 2, 2017
656
FL
I wanted to clean up the shop of "leftovers" so I did an oil change last year with 4 different brands and grades of oil:jawdrop2:

Car is running same as always today. Oil looks perfectly normal.
I believed the 7 quart story too. Last oil change I only used 6. The level is near the middle of F and L - I think that's OK.
 
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Jkb242

Original poster
Member
May 19, 2019
239
CLT
There would be no problem with mixing the two of them, I've done it on my 5.3 without any issues and in the past with my other 4.2's. Does the line read full when you put in 6 QTs? GM calls for 7.
I thought it was 6Qts for the 4.2 so I’m not certain I know mh 5.3L requires 7qts. Thanks for confirmation I suspected that would be the case but wanted at least to do a sanity check. All the best!
 
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Dec 5, 2011
574
Central Pennsylvania
You need a total of 7 quarts if you're replacing the filter as well. I've actually had oil changes where I've put in a little over 7 quarts.
 
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Jkb242

Original poster
Member
May 19, 2019
239
CLT
You need a total of 7 quarts if you're replacing the filter as well. I've actually had oil changes where I've put in a little over 7 quarts.
For the 4.2L engine? Wow!
 

Sparky

Member
Dec 4, 2011
12,927
I thought it was 6Qts for the 4.2 so I’m not certain I know mh 5.3L requires 7qts. Thanks for confirmation I suspected that would be the case but wanted at least to do a sanity check. All the best!

My 5.3 in my Silverado calls for 6 qts. My 4.2L in my old Trailblazer called for 7.
 
Dec 5, 2011
574
Central Pennsylvania
For the 4.2L engine? Wow!
The oil pan on these is huge. Also, it uses oil pressure for the Variable Valve Timing system, so that may have something to do with it. When I buy oil I usually buy 3 "5 quart" bottles and it's enough for 2 full oil changes. I've been using Walmart's High Mileage Full Synthetic exclusively for about a year now and have had good results. I still use a good oil filter with that, though. Mobile 1 oil filters can be gotten from Walmart as well.
 

bfairweath

Member
Oct 20, 2013
95
Neenah, WI
OP - Where do you live? If you live in a cold climate, I would get that 10W-30 out of there before the weather gets cold. Probably be okay for the summer months.
 

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