Higher Engine temp = more oil burnt ?

[stuartgb100]

Hmmmm .......... here's the situation:

Standard engine spec Sprint, bought about one year ago.
Not happy with the high running temp (200 deg F when moving).
Engine leaks just a little, but dipstick level drops noticeably after 100 miles.
Engine rebuilt < 10k (receipts to show) - reputable usual suspect
Compression is 195 - 200 across the cylinders.

So, I decide the temp is too high (I always ran cooler with Cortinas and an Escort), and did as follows:

Change to a 72 degree thermostat
Swop narrow rad for a full-width rad (rebuilt + an extra row of cores)
Fit a 9 inch Kenlowe fan (switched to cut in at 190 derees)
Fit a cardboard scoop to deflect incoming 'cool' air above the steering rack

Now, the engine runs around about 180 degrees under load, and the fan soon cuts in when stationary and drops the temp (even in current 27-35 deg C temperatures)

Question: I'm now using virtually NO oil at all. 400 miles and it's still at Max on the dipstick. Only minor drips on the garage floor.

BTW: not losing any coolant, either.

So is there a moral here, or just some 'fluke' of circumstances that I should be grateful for?

Regards,
Stuart.

[twincamman]

--my 7 and ?lan run a little hotter in the summer too ----[summer in England must be just above freezing ]-----85 and 90 degree temps on the highway causes plus 90 degrees Celsius on the Gauge and in the fall and spring its 90 c constantly -- the fact your ?lan doesn't embarrass its self by losing its vital fluids in public impresses me greatly mine has no self respect that way --ed

[rgh0]

Stuart

Rapid loss of oil on the dipstick or periods of no oil loss often relate to the build up of other fluids such as water and petrol components and their evaporation from the oil.

A period of short trips with the engine mainly at low temperatures can lead to blow by gases containing water and unburnt fuel condensing and building up in the oil. A period of hot high temperature operation can boil all those components out of the oil again in a short time and lead to an apparent sudden loss of oil.

Oil itself also contains a range off different molecules and the lighter ones can also boil off at higher operating temperatures, especially for the cheaper and less carefully refined oils. Modern synthetic oils have virtually no evaporation loss in normal use.

The actual consumption of oil by burning it in the combustion chambers should not be significantly affected by a 20 degree change in water temperature. The amount of oil getting into the combustions chambers to be burnt is governed by leakage clearances down the valve guides and how effective the piston rings are at scraping oil off the bores. neither of these factors is signficantly affected by such a small change in temperature.

The moral is if you do a lot of short trips when the engine does not get hot and boil of the contaminants then change your oil regularly to drain out the contaminants with the oil.

regards
Rohan

[stuartgb100]

Rohan,

Thanks for that.

I (almost) never use the car without getting it up to temperature, and even a 'short' trip is at least half an hour - generally most of the time at, but not over the maximum legal limit (honestly).

As for oil, I use Castrol Classic XL 20W/50. Not particularly cheap, but to me it's a bit like the choice of tyres .... too cheap can be a false economy,
IMHO.

Perhaps changing the oil more often than the recommended interval would not be a bad thing, as you say.

Regards,
Stuart.

[thor]

I actually have the same situation, with hardly any oil consumption or water loss, and keep VERY quiet about this.
This thread must be KILLING the 70-80% here who have the normal situation of oil burning/loss and/or other fluids dissappearing.

I feel this is a case of finding a problem that isn't there... DO NOT EVER EVER complain of an old Lotus NOT losing oil or water, I repeat DO NOT!

[M100]

DO NOT EVER EVER complain of an old Lotus NOT losing oil or water, I repeat DO NOT!

I did, and couple of days later I grounded the car at speed and ripped a hole in my sump.