2mahams Report post Posted December 21, 2014 Ok need some advice here, going on a trip in 2 days and checking fluids and the reservoir is at min. I have a CAT C7 rear radiator and the antifreeze looks green even though the tank is stained red. I bought this used back in August, I changed the oil and filter. Other than that, I was going to waiting until after the new year and take it to Freightliner for service since I don't know what has been done to it by previous owners. I have some Prestone EL for light trucks but don't want to mix if it is wrong, any help out there as I don't have time to get a antifreeze change. Driven it a little over 700 miles since I bought it. Thanks Share this post Link to post Share on other sites
wolfe10 Report post Posted December 21, 2014 There are three basic types of coolants: 1. Regular car coolant (like the vast majority of Prestone products. 2. Low silicate for diesel with added SCA (Supplemental Cooling Additive). 3. New generation OAT--based coolants. Sadly, coolant color is not consistent across brands. Best advice-- check freeze point (test strips from most diesel shops). If topping off with distilled water will still keep your freeze point comfortably below ambient temperatures, add distilled water. SCA's can also be tested, but if you are going to change the coolant in a month or two, with the parent bore C7, I wouldn't be too concerned about the SCA's. The reason I suggest distilled water is that it is compatible with any coolant you have in there. If you do need to lower freeze point, I would go with one of the low silicate coolants-- use concentrate to make a lower freeze point. Share this post Link to post Share on other sites
2mahams Report post Posted December 21, 2014 Thanks Wolfe10, I had a new glass bulb anitfreeze checker and it said good to -40 so I added about 3/4 gallon distilled water, that should get me through until I take it to Freightliner for service. I'm new at this DP as I had 2 Class C MH's which I did a lot of work on. Share this post Link to post Share on other sites
huffypuff Report post Posted December 21, 2014 Minimum level in the reservoir is fine if it is cold as that is more likely the cold mark. If you fill it to the max it could spill over when you go up the next steep mountain grade. My coach found its normal level right between the full and minimum mark cold. It is good to know I'm not polluting the road. Share this post Link to post Share on other sites
