rear main/oil pan leak got worse, move to 10w30? or switch to conventional?

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jalikaria24

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Sep 23, 2017
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hey guys! so my 03 hummer h2 has a rear main/oil pan leak. i noticed it had it in like september and it was slow leak but that also could be because the temps in alberta were colder. i was running 5w30 synthetic like always. the dealership i got my oil change noticed it and said they cant tell if its the rear main or if its the oil pan, thye would have to do a die test and they quoted laber at minimum $1200.
i decided to leave it alone since at first it was barely leaking. like over 6000km oci, my oil level would go from full to half way in the dip stick. our winter here was super cold so i didnt notice anything unusual for oil level in the winter.

but now its spring/summer and i noticed that i lost about a quart of oil over the past 3 months i would say which is way more then what i was losing in the past. i also noticed the puddle under my vehicle is larger then it was before. i tbh will only be driving this vehicle for the next 6 months and then it will either be parked or rarely driven so i dont really want to spend all that money on the labor to fix it.

i don't think my vehicle was running full synthetic its whole life. i am certain it was running the semi synthetic at the gm dealership for the longest time until they switched to dexos gen 2. but i know for the last 50,000km i have run full syn so maybe that made the leak worse.
i always just follow the oil life monitor in my truck even tho i run full syn with really good filters. so i guess i could come to conventional for the summer.

i was also thinking of running a hm oil. so right now, since the temperatures are always 20 celcius and above this summer and it wont be getting cold for another like 4 months atleast, i was thinking of maybe running a 10w30 hm or something? or should i NOT do that since ive always run 5w30 in the past? because if i do drive this in the winter i will have to go back down to a 0w30 or a 5w30 because it is regulary -30 celcius here in alberta during the winters. or maybe i should run conventional oil?


i am also in canada so i dont think ill be able to find a 10w40 easily. seems like these are all i can find
i guess my choices are:
motomaster5w30 hm conventional (since i do low oci it should be fine)
motomaster 10w30 hm conventional (since i do low oci it should be fine)
quaker state 5w30 full syn hm (they make this full syn hm just for canada i think)
10w30 castrol gtx semi synthetic
valvoline maxlife red bottle hm syn blend 5w30




thanks!
 
Last edited by a moderator:
I would try a 5w-30 HM oil. Mobil1 HM 10w-30 worked very well for me on rear main seal seeps. There is no cure for an oil pan leak and repair is the only option (and a lot cheaper than a rear seal repair).
 
I'm told those LS engines have a Teflon rear seal so.the usual.HM.Oil or AT-205 Reseal won't accomplish anything. Maybe a 15W-40 HDEO like Shell Rotella, Mobil Delvac 1300 or Chevron Delo 400 during the summer and the 5W-40 Synthetic version during the winter will slow the leak.
 
thanks for the reply! should i do 5w30 hm conventional or full syn? maybe the conventional will be slightly thicker?
 
for the 5w30 here is some data i found for viscoisty:

motomaster 5w30 hm conventional:
at 40 celcius: 64.6 at 100 celcius: 10.67

quaker state full synthetic hm 5w30
at 40 celcius: 60.71 at 100 celcius: 10.77

mobil 1 high mileage synthetic 5w30
at 40 celcius: 70 at 100 celcius: 11.9

mobil 1 5w30 what i have in it rn (just the oridinary grey bottle)
at 40 celcius: 64 at 100 celcius: 11.1

valvoline hm red bottle syn blend
at 40 celcius: 65 at 100 celcius: 10.9



or should i move to a 10w30?
 
With a valve cover leak on my mother's car switching from Motorcraft synthetic blend 5w20 to Supertech "conventional" 5w20 (also a blend) high mileage cut oil consumption fairly significantly. I would top a quart off at 1500-2000 miles, and I would drain out about 4.5 quarts. This time my only top off quart was at 2800, dipstick lost maybe a quarter of a quart at 4500 miles, and I drained off a 100% full 5 quart jug. It's a 6qt sump car.

I'd personally try a conventional or synthetic blend high mileage 5w30, worst case, nothing happens, best case you solve a consumption issue.

In summer I'd like to do the valve cover gaskets, but it's pretty involved on that car since you need to pull the upper intake manifold off and a strut brace. Also change the PCV when I'm there, too.
 
celicaxx said:
With a valve cover leak on my mother's car switching from Motorcraft synthetic blend 5w20 to Supertech "conventional" 5w20 (also a blend) high mileage cut oil consumption fairly significantly. I would top a quart off at 1500-2000 miles, and I would drain out about 4.5 quarts. This time my only top off quart was at 2800, dipstick lost maybe a quarter of a quart at 4500 miles, and I drained off a 100% full 5 quart jug. It's a 6qt sump car.

I'd personally try a conventional or synthetic blend high mileage 5w30, worst case, nothing happens, best case you solve a consumption issue.

In summer I'd like to do the valve cover gaskets, but it's pretty involved on that car since you need to pull the upper intake manifold off and a strut brace. Also change the PCV when I'm there, too.
Click to expand...
When the valve cover gaskets were leaking on my old Chevy 305 V8 it was going through a qt every 2500 miles or so and they were leaking severely. After I replaced the valve cover gaskets it still used the exact same amount. I've never had valve cover gaskets leak enough to go through that amount of oil.

Not that it's not worth fixing if it's leaking enough to smell like oil (like mine was), but I'd be worried it would have no effect on oil loss.
 
350Rocket said:
When the valve cover gaskets were leaking on my old Chevy 305 V8 it was going through a qt every 2500 miles or so and they were leaking severely. After I replaced the valve cover gaskets it still used the exact same amount. I've never had valve cover gaskets leak enough to go through that amount of oil.

Not that it's not worth fixing if it's leaking enough to smell like oil (like mine was), but I'd be worried it would have no effect on oil loss.
Click to expand...
Supertech really improved the smell, it's mostly gone now. Before, it would smell even after short 5-10 mile drives.
 
apollo18 said:
hey guys! so my 03 hummer h2 has a rear main/oil pan leak. i noticed it had it in like september and it was slow leak but that also could be because the temps in alberta were colder. i was running 5w30 synthetic like always. the dealership i got my oil change noticed it and said they cant tell if its the rear main or if its the oil pan, thye would have to do a die test and they quoted laber at minimum $1200.
i decided to leave it alone since at first it was barely leaking. like over 6000km oci, my oil level would go from full to half way in the dip stick. our winter here was super cold so i didnt notice anything unusual for oil level in the winter.

but now its spring/summer and i noticed that i lost about a quart of oil over the past 3 months i would say which is way more then what i was losing in the past. i also noticed the puddle under my vehicle is larger then it was before. i tbh will only be driving this vehicle for the next 6 months and then it will either be parked or rarely driven so i dont really want to spend all that money on the labor to fix it.

i don't think my vehicle was running full synthetic its whole life. i am certain it was running the semi synthetic at the gm dealership for the longest time until they switched to dexos gen 2. but i know for the last 50,000km i have run full syn so maybe that made the leak worse.
i always just follow the oil life monitor in my truck even tho i run full syn with really good filters. so i guess i could come to conventional for the summer.

i was also thinking of running a hm oil. so right now, since the temperatures are always 20 celcius and above this summer and it wont be getting cold for another like 4 months atleast, i was thinking of maybe running a 10w30 hm or something? or should i NOT do that since ive always run 5w30 in the past? because if i do drive this in the winter i will have to go back down to a 0w30 or a 5w30 because it is regulary -30 celcius here in alberta during the winters. or maybe i should run conventional oil?


i am also in canada so i dont think ill be able to find a 10w40 easily. seems like these are all i can find
i guess my choices are:
motomaster5w30 hm conventional (since i do low oci it should be fine)
motomaster 10w30 hm conventional (since i do low oci it should be fine)
quaker state 5w30 full syn hm (they make this full syn hm just for canada i think)
10w30 castrol gtx semi synthetic
valvoline maxlife red bottle hm syn blend 5w30




thanks!
Click to expand...
Have you tried Blue Devil Rear Main sealer? I know many guys who have used this product for rear main seals and it worked well. No special oil is needed & the product is guaranteed to work or your money back.

Link to the product page- https://gobdp.com/product/rear-main-sealer-00234/
 
celicaxx said:
With a valve cover leak on my mother's car switching from Motorcraft synthetic blend 5w20 to Supertech "conventional" 5w20 (also a blend) high mileage cut oil consumption fairly significantly. I would top a quart off at 1500-2000 miles, and I would drain out about 4.5 quarts. This time my only top off quart was at 2800, dipstick lost maybe a quarter of a quart at 4500 miles, and I drained off a 100% full 5 quart jug. It's a 6qt sump car.

I'd personally try a conventional or synthetic blend high mileage 5w30, worst case, nothing happens, best case you solve a consumption issue.

In summer I'd like to do the valve cover gaskets, but it's pretty involved on that car since you need to pull the upper intake manifold off and a strut brace. Also change the PCV when I'm there, too.
Click to expand...
I've also noticed a reduction in consumption switching from mobil 1 to superteq 10w30 in a Buick ultra.
 
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