I have a CAT C-7 diesel engine in my MH.  I have to check the coolant for proper SCA (rust inhibitor) levels every six months, drawing a tiny sample from the radiator drain pet****. 

For those of you with diesel engines that require SCA's, what test strip do you recommend and what is the best, most accurite way to use them?

I picked up some test strips from my local Freightliner dealer, the strips test for 3 differant chemicals, but my CAT only requires 2 of those chemicals.  I don't want to make any mistakes here and allow corrosion of my engine block to take place.

Best Regards! 

Snipe: This is not an answer to your post only a cautionary note to other diesel owners, especially the big blocks, that there are coolants out there that do NOT require SCAs (Supplemental Coolant Additives). These are the OAT type coolants (Organic Acid Technology) and one particular brand in some MHs is called "Final Charge." These coolants need no SCAs, have no routine maintenance save for only the addition of a recharge chemical at 300,000miles. Also note that some systems add SCAs directly to the coolant and some add them using SCAs imbedded in the coolant filter.

My point: Know exactly what coolant is in your rig and what its specific maintenance requirements are. It’s not as easy as it used to be. Also note that although coolant color USED to be a standard for determining what the coolant is, the colors have now mingled somewhat and although generally it MAY be OK to add the same color coolant, it is BEST to know the exact product in your system. Click the link for a brief report from the filter manufacturers council. Yes, you can change coolant types by flushing and filling if you so desire.

Now back to what test strips?

BTW: The SCAs (additives) do a lot if critical stuff, rust protection and metal erosion protection being just one. Their main purpose in diesels is to prevent coolant cavitation and subsequent destruction of the block and wet sleeves.

Typically, if your engine has a coolant filter attached, the filter will supply all the SCA you will need between recommended coolant filter change intervals. Still a simple test with the strips is easy and quick and reassuring. I use strips I purchase from Cummins. They are a little expensive but so is a hole in a sleeve. The strips come with instructions. Be sure to read them and understand what they are saying before putting the coolant on the strip because it is all a timed event. Our current coach engine does not have a coolant filter. I discussed this with Cummins reps and they told me that the newer computer controlled engines don't need the SCA anti-cavitation protection like the older engines did. Well, I just don't know whether I buy that totally or not. If that is totally true then why is it in there? I still keep the SCA level in the green, but I have observed that this engine. (05 Cummins 8.3 liter) does not erode the SCA level like my previous engine (01 Cummins 8.3 liter) did. Even thought the 01 had a coolant filter attached. I am going to have the coolant filter added to this engine as soon as I can. It just gives me a better peace of mind feeling and the filter will help keep the coolant clean too. It isn't just there for maintaining SCA coolant levels! JMO

Paul,  Your questions are frequently addressed on the Frieghtliner Owners Club forum. Rather than repeat all the details, here is a link  

http://www.freightlinerchassisownersclub.org/coolant_info.htm

Jim