Im wondering if mixing a quart of 40 weight oil with 2.5qt's of 30 weight can cause my engine to bog at low RPM's? I understand that my head gasket is probably going bad because theres always been a hint of white smoke since i got the car, but it hasnt changed for the worse.

Heres what i know: LS motor w/ 150Kmi. The car ran fine before i noticed the oil was super low (burns oil pretty bad, not my fault). I added a quart of 40weight (desperation) and 2.5 qts of 30 weight. At the same time the temperature outside dropped drastically, and since then the car has been bogging at low RPM's. I added bars leaks to my radiator (in hopes it would fill in any gaps in the headgasket or block...as advertised) which did nothing. The coolant is still clear (green), not muddy.

Should i try replacing the oil before having the head gasket replaced. This is a beater car but id like it to last until May when i graduate. I dont have many options here or do I? Any advise would be great...the sooner the better, id hate for my car to break down only to find the solution to the problem. Thanks in advance

 

how drastic of a temperature change?? you should go ahead and do an oil change just to be on the safe side and keep up with your maintenance.

 

The temp gauge, before, i think read about 1/4 now when i drive its a bit past that maybe at about 1/3 still not half way though. The check engine light and maintenance lights have not come on either. Today when i got home, the temperature is in the 60's today and i could hear the coolant boiling in the overflow tank; not sure how normal that is.

 

as long as youre withing a safe operating temperature you should be good unless your coolant sensor is bad. i lived in indianapolis and drove my gsr thru all sorts of different weather ranging from 100 degrees to below 5 degrees. check your spark plugs and see what they look like.

 

Straight 30 and 40 weight oil in the engine? That's just asking for trouble, as our cars were designed for 10 weight oil...

Now, 10-30 and 10-40 are both 10 weight oils, just one will maintain viscosity better under higher temps.

 

I believe i added to 5w-40 to the 5w-30; thats what i meant

 

Anyway, I talked to my friend and i think hes goona help me change the headgasket this weekend. Life saver; i cant afford another car at the moment...just need this to last until May's TL arrival

 

I am glad to see that you are doing the head gasket... if you are boiling coolant thats a tale tale sign of a head gasket gone bad. As for the oil they don't make 5-30 and 5-40 so it must have been 10-30 and 10-40 and in my experience that would make no difference at all to the way your car runs... would I do that on a regular basis... NO no need use the same oil LOL. I am a 10-30 guy myself. The head gasket install is really simple just make sure you take your time and make sure the timing belt is installed right as well as make sure the timing is on... That could make things out to a bad bad day if you are off and meet the pistons and valves. They are not friends!