I just had a question for the the oil weight in an LT1. Can I run 10/40 in a LT1 with 138K or would it be safer to run 10/30? I only will run the car in warm weather. Just a general question as it says 5/30 on the filler cap.
my motor has bout 156k on it and i use mobil1 5w30 in it...i love synthetics but i dont suppose it would hurt and give a lil more protection if u went with 10w30...in the summer the oil will kinda tend to be thinner during a first start in cold due to the heat and i honestly would use a synthetic based oil imo....better protection, last longer, and can help ur mpg..hope this helped
ive used mobil1 since ive gotten the car but i changed my motor and used it in that...in my imo if ur worried about leaks id use a heavier weight but the right way i would just fix the leak problem..but if ur motor is stock i would just use 5w30 or 10w30
If a motor starts to leak because you put synthetic in it, it already had problems anyway. It's mostly an urban legend with modern engines that you can't run synthetic if you normally ran conventional.
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Synthetic causing leaks was due to older designs of gaskets, from engines prior to 1988, so with newer gaskets there is virtually no chance of leaking due to changing from conventional to synthetic. I have 234lk on my lt1, and I run 5w30 synthetic in my car. Have no problems with it, and great oil pressure. So running heavier weight oil will not give better protection (unless there are internal engine problems), and will chew up some hp in the process to turn the pump to pump the thicker oil.
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I would recommend a high mileage oil for your LT1. I think you would be satisfied with Mobil 1 High Mileage 10w30. It has a lot of calcium for cleaning and a higher viscosity formula, so its a thicker oil. It also will help prevent and stop very minor leaks. It wont really hurt to run the 10w40 in your LT1, but it wont provide any benefits over 10w30 or 5w30. Also the first number (0,5, or 10) only really applies to cold start ups anyway. So if you operate it in a warm climate dont worry about if its 5 or 10.
Valvoline Maxlife Full Synthetic 10w30 or 5w30 is also a good oil. But I prefer the Mobil 1 High Mileage. If you are like me and want VERY detailed information on different oils, then read up at bobistheoilguy.com But I will tell you that it can lead to hours upon hours or reading about motor oil!
Depending on the temperature of your area. Lets say you drive in mostly 40* or warmer a 15W40 would be your best bet. Thicker oils do not fill voids. If the bearings wont hold an oil film the bearing clearance are toast. Gm does not recommend 10-40 oils because its VI ratio is to broad. Never use an oil with over a 2 step Vi ratio. 10w -30 is fine in colder winter driving but for warmer high speeds a 15W 40 is the ticket in my view.
5w30, and 10w30 are BOTH 30 weight oils. The 5w has the better cold start viscosity. Otherwise at 100C, they are both rated as a 30 weight range oil. Same as 0w30. Last I checked the owners manual in the car does recommend 10w40 at certain temps.