I usually put 10w-40 in my car during summer, but since its winter I wanted to bring it down to 10w-30, but I had a free coupon for oil change/filter/lube at merlins so I brought it there and they put 5w-30 Mobil1 in it. My car has 100k would using 5w-30 for just the winter be ok? Usualy I feel more comfortable using higher wieght oil, I duno why.

 

5w-30 is what GM speced in the LT1 not that it is best but it is what was speced and will be fine, many an LT1 has lived a long life with nothing but that exact oil and it is actually very thin as even synthetic 30wts go. Arguably too thin for long term performance use but in thins instance I would leave it be till it is ready to be changed based on milage or time. The comments on being thin arre specifically for M1 5w-30 and 10w-30 and DO NOT necessarily aply to other Xw-30 oils, one popular 0w-30 is actually much thicker and returns better analysis results.

 

I run M1 10-30w all year round in NC. I was running M1 5-30w and on cold winter morning starts it would tick at the lifters for the first little bit. Try 10-30 and go from there is what I would recommend. My co-worker had the same tick in an LT1 caprice and 10-30w cured his also.

 

My original stock 350 had nothing but 5W-30 dino used in it, changed every 5,000km (3,000 mi). After 200,000km (125,000 mi) of fun, when it was torn down for the 383 build up, all of the internals and bearings were well-worn, but still in reasonably good shape.

 

10w-30 DOES NOT mean thicker at operating temp than 5w-30 I know that contradicts what most of you "know" about oil but it is fact. Amsoil 0w-30 or Castrol Syntec 0w-30 are both much thicker than M1 5w-30 or 10w-30. You pick the first number to support whatever your expected cold start conditions will be the owners manual states even 10w-30 is fine down to 0F, no harm in running something rated for much colder starts though. The second number is the viscosity RANGE the oil falls into at operating temps again RANGE not an exact measurement the M1 5w-30 and 10w-30 fall right near the bottom end of that range nearing 20wt. The other two I listed come in closer to 40wt even though they are 0w. The 0W-30 German made Castrol Syntec in particular is putting out awesome analysis numbers in all weather from autoX in the heat of summer to the bitter cold of winter. Not saying everyone has to go through the hassle of finding it just saying it throws all the 10w-30 is better in summer than 5w-30 ignorance out the window. I use ignorance to describe the lack of knowledge and generally poor info out there about oil not as an insult.
If someone tells you to run 5w-30 in winter and 10w-30 in summer you really need to think twocebefore listening to them because they are demonstrating how little they know on the subject.

 

For what it's worth, I use 5w-30 year round in my LT1.

I actually use 0w-30 year round in my Subaru, which is an entirely different car of course, but the point is that you should be deciding what oil to use based on what your oil pressure gauge is telling you. You need a REAL oil pressure gauge of course, that reads in pound; and you want at least 10pounds/1000rpm. Going much beyond that just increases you pumping losses and generates heat.

 

Again one brand 0w-30 can be thicker than anothers 10w-30 or it could go the other way.

 

Im running 5W30 Mobil 1.

I dont know if jumpin to a 10W30 would be right for me, but from what I've seen on the board, with Mobil, you should go with a 10W30 ...

the best oil seems to be the GERMAN made Castrol Syntec. However nowhere by me carries it

For what its worth: On my car, in the middle of summer, idling in traffic, I still have about 20-25 on my oil pressure guage. Granted, I do have a big oil coller mounted in the very front, but still ... at cruising speeds ( 1800 to say 2500 ) I have at least 40. This is with a low mileage motor also ... 17K origional miles

 

I use Mobil 5w-30 year round in both of my vehicles.

The following is from the owners manual (1995). The same information can be found in the GM Service Manual. For the V8 info, it is exactly the same as that found for my 2002 Silverado.

Please use the following as guidance and come to your own conclusions: Oil Info

 

Where can the 0w-30 German Castrol Syntec be purchased? Thanks.

 

The German Castrol is nice, but to go out and find it and go thru the BS I've finally said screw it, back to the ole Mobil 1.

FWIW I run 5w-30 Mobil 1 for 7000-8000 miles in my LS1 and the motor loves it, throw in a good filter and it's even better.

Also I like to spec the first number on motor builds on how the oil pressure is at startup.... for where I set bearing clearances 5w works great, and you can even run 0W. So after breakin 5w-30 M1 is what I recomend on something that would cost me a load to replace if I was wrong.

Bret

 

you have to look around i got mine today at my local autozone i was lucky it was even on sale, its in black and reg lettering just look on the back of the bottle to make sure it says made and imported from germany and NOT made in u.s

 

Bret what kind of pressure do you look for on a cold start ?

My car will idle at about 40 PSI cold start (Like say 40 degrees out side ... and then once its hot idle at about 25) This is with 5W30 Mobil 1 ... I keep thinking maybe try the 10W30 since it tends to be thin oil for its ratinjg though but I dont know ...

 

I like it to be as close to the hot idle as possible. I normally see areound 35-40psi hot at idle with a max of 55-60psi. Might want to try the 5W-40 or 0W-40 with 25psi at hot idle to see what you get then.

Bret

 

with whatever oil the guy put in before i had about 40-50 psi cold start with just shy of 20 @ idle, i put in the Castrol Syntec german 0w-30 and my oil pressure actually increased, 55-60 psi oil pressure with 30-40 idle hot