ok well i went to start my truck to move it to a diffent parking space and when i started it but not immediatly it started knocking about 3-5 after i started it for about 5 seconds. im using 10w40 Castrol high milage oil with 1q of Slick 50. is this bad? is running it without a thermostat hurting it? and if maybe by chance i need a new oil pump would a high output pump work best? and if so which Melling pump should i get? last but not least truck has 224k on it. would switching to synthetic 5w30 castrol edge help in this startup knock? any ifo will be very much appreciated.

 

10w-40 is not the recommended oil for that year blazer.. i`m using 5w-30 Castrol Edge in mine since they first came out with it and i`ve had no problems with any engine noises. as far as the thermo goes why run it without it? your going to overheat in hot weather.....

 

im just wondering if it will hurt the motor now without a stat and what could be causing my knocking on startup

 

well lets see here, no thermostat + engine overheat + incorrect weight oil = engine failures such as warped head, including other damages if not detected early enough...do it right the first time and be safe not sorry..

 

ok well ill throw a 180 stat on tommarow and should i switch to 5w30 castol edge at 226k? i know its not the original engine but i bought it last month at a police auction with a lean condition fixed by putting all new vac hoses

 

195 deg thermo is whats correct for these engines. putting the correct oil in the motor will most likely lengthen the life of the motor regardless of mileage, i now have almost 107,000 on my motor..These blazers are like girlfriends and wives, if ya don`t give them what they need or want, they break down on ya.

 

but is switching to synthetic a good idea at this millage? im running reg oil right now. i also added u on msn for faster info

 

I'm running 20w-50 (the only stuff I had on hand when I got my truck) and I've got absolutely no knocks whatsoever.

Any sort of knocking is not good.

 

20w50 is what i run in my sonoma with 242k on it with no knocks. just alittle initial start-up lifter tap but not bad.

 

Don`t quote me on this because i`m not 101% sure, but from i`ve been told you can go from reg oil to synthetic but once you use synthetic you can`t go backwards.. Maybe someone else here who is an up to date mechanic can confirm this. synthetic oil may even be better for your engine at that mileage, but i`m just guessing at that, go to the store and read the label on the oil container and see what it says.