Expert: Josh Fields - 4/24/2006

Question
I have a 1992 318ic. Lately my thermostat reading has risen increasingly higher. I try to lower this by running blower on hot, or AC. Sometimes this works.  At present it has never overheated. What coolant should I be using, in the Florida summer?While I am with you, what motor oil should I use? I have been using 5w-30.

Answer
Michael,
First off, your over heating problem is likely due to a faulty thermostat or a worn fan clutch.  Both of these are pretty simple fixes.  When I say thermostat, I'm talking about the valve-like mechanism that controls coolant flow, not the actual gauge.  The coolant you are using shouldn't matter, however I would always use normal coolant and not the "Dexcool" coolant.  You will know it's the wrong kind because it will be ORANGE instead of green.  Always use Green coolant and follow the mixing instructions on the bottle (If applicable).  If you mix the coolant with water, make sure to use distilled water, as it conains less minerals, so corrosion and deposits will be less.

 As far as motor oil goes, you live in Florida, so you "could" run a thicker oil.  Thick oil provides more protection than thinner oil.  There are a couple reasons to run thinner oil, temperature, and fuel economy.  If you live in Wisconsin, you are likely to have drastically different winter temps than florida.  So a thinner oil should be used in cold weather, as it doesn't gel as bad.  

 As a rule of thumb you should follow the owners manual and it's oil recommendation.  It probably comes down to preference and safety.  I live in GA where we have slightly lower temperatures than Florida, but I still run a thicker oil than recommended.  The most important thing would be conventional or synthetic oil.  I run ONLY synthetic oil.  Mobil-1 is the leading brand and that's all I run.  I run 15w-50 for extra protection.

 It's up to you what oil you run, but personally in Florida you wont have freezing problems, so there is no reason to run a 5w-30 weight oil.  I would at least run 10w-40.  If all else fails and you cant decide, run what the manual says, only use synthetic oil.

 Hope this helps,
 Josh