Coolant and Flushing for a 1965 Mustang


What is the best coolant for a Mustang 289 engine running in a 1949 Ford. Things have changed since 1965 and I’m confused. The good news is that it doesn’t overheat. I’ll try to keep the questions short.

1) Should I use ethylene glycol and water or propylene glycol and water, or something else?

2) Is Non-Aqueous Propylene Glycol offered by Evans Cooling Systems really different than propylene glycol? If so, is it worth the extra cost?

3) Based on the preferred result from questions 1 and 2, how often should I flush the system? My Toyota Higlander says flush at 100,000 miles :slight_smile:

Thanks for your help. Dave


Back in 1965 they only had ethylene glycol antifreeze – the green stuff. The 50-50 mix was standard. I believe that Prestone’s yellow stuff will serve you well. You have no reason to use anything else.

Evans Cooling systems is very coy about telling anyone what’s in their non-aqueous propylene glycol formula. Apparently they found some diluent other than water but they won’t tell us what it is, so no one else can evaluate their claims. Frankly, I wouldn’t touch it.

The flush interval for my car is every 90,000 miles or three years. Again, that’s a good guideline for most automobiles.


With old style antifreeze I believe the recommended change interval is every 2 years or 24K miles.


Is there any reason to use the old style antifreeze, ethylene glycol? I understand it can turn to a gel hence the 2 year flush interval.


Get some Zerex Original Green unless you have an aluminum radiator or heater core. Even if you do, the Green will work. If you do have aluminum, I would suggest their G-05. G-05 is a Ford formulation used in their engines with mixed ferrous and aluminum engines and cooling systems. With any coolant, changing the coolant every two years cheap compared to ruining the stuff it comes in contact with. Mix the coolant with tap water if it is not hard. If you have a lot minerals in your tap water, do your final fill with coolant and distilled or deionized water.

Even Zerex’s Original Green has reduced silicate. The silicates are what causes the gelling problems so reducing them reduces the gelling. Note that the silicate is there because it is a corrosion inhibitor. They mix in others as well.

Last I knew, all manufacturers fill their vehicles with ethylene glycol-based coolants and disrecommend propylene glycol.


Use what ever is on sale at Wal-Mart and it will be 5 times as good as what Ford originally put in your 289 which apparently survived all these years with God-knows-what in the cooling system…


Gelling of a coolant system occurs when too high of a concentration of antifreeze to water is used. That’s why all producers of antifreeze have made the 50/50 mix a standard.