I usually add coolant only to a level that covers the core when cool.
Expansion with heat makes sure the full core is effective for cooling and
there is still some room for additional expansion due to steam in the block.
Sometimes the level drops below the top of the core so I check the temp
gague occasionally and add water if it’s running a few degrees warmer than
normal. There have been times in 90+ weather that the temp has risen to just
below 100C but it always levels off there as the additional heat loss due to
boiling creates a plateau due to the extra energy required for the change of
state.
I suspect the manufacturers recommend two years to sell more antifreeze.
Maybe there is some scientific basis for two rather than 3 but I’d like to
see it. What is it that degrades over time? (heat transfer, anti-corrosion,
viscosity, acidity, etc.)
Paul,
If you are using antifreeze only for storage, I’d bet the 2 year rule does
not apply at all. Probably the shelf life in the jug would be appropriate if
there is one as the heat cycles must have a lot to do with life in the car.
In reply to a message from Bruce Cunningham sent Wed 29 Dec 2010:
Gents,
It is the anti-corrosion spec that goes out.
It may be that the coolant test strip manufacturer’s are
part of a scam, but I tested my antifreeze after 2 years
with the test strips and basically DOA. So the green stuff
last 2 years. Didn’t make a record of what the specific
readings were, I think it was out of spec across the board.
I got some test strips from Mike Frank - possibly other
sources.
If the antifreeze is on the shelf, probably OK but ecven if
just sitting in the block/head/radiator one could I think
assume that the anti corrosion properties, while perhaps
less stressed without being heat cycled, are still subject
to degradation - the strips will tell you.
Regards
Keith–
The original message included these comments:
I suspect the manufacturers recommend two years to sell more antifreeze.
Maybe there is some scientific basis for two rather than 3 but I’d like to
see it. What is it that degrades over time? (heat transfer, anti-corrosion,
viscosity, acidity, etc.)