Too low engine temperature with SAE 50 grade

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Hi,

my car originally calls for engine oils typically in the range of 10W40 or 15W40. I've run on 0W30, 10W40 and for a loong time 5W40 without any problem. Recently I switched to a 5W50 100% synthetic oil (think it's rebadged Mobil 1) which has been top rated in a review. I was motivated to use this oil because it was rather cheap (rebadged but it is Mobil1 oil old formula) and because my car has now 240,000km so I assume that clearances are bigger than when new...

I've run 6000km with this oil until now and I've seen that the engine temperature is almost 10°C lower than with the 5W40 I used before!!! This may sound good but my engine runs at 70°C, is it too low???? And the engine takes much more time to heatup in the morning: maybe this is not good too no?????

I also see that the mpg is lower than before as I burn 1liter/100km more than I did with the 5W40. I assume this is due to the elevated SAE 50 grade but is it normal that it does such a big difference?

My main concern is with the "too low" engine temp. Is it a problem or a good thing mainly considering the fact that the heatup time is much more longer now?
 
My kneejerk reaction to the temperature issue is: Has the thermostat been changed lately? 50 weight will generally reduce efficency somewhat. This will be aggrivated if the coolant is at a lower than normal temp due to a bad thermostat. Are your drive times long enough for a thorough warmup? Good Luck. Rickey.
 
Thanks Rickey! Actually the thermostat has never been changed (I plan to change it soon) but this low temperature "problem" really started right after changing to this 5W50 oil so I assume that it is related to oil.

My drive times are more than sufficient to warm the engine. Actually with the previous 5W40 oil, I got 78°C on normal drives and 83-87°C on highways at high speed but most of the time the coolant temperature was 78-82°C. Now right after having switched to this 5W50, I run at 69-70°C on normal drives but on highway the temp grows up to 74-78°C.

Do you think it can really be the thermostat? Anyway I think I'll change it since it has now 240,000km so it has lived enough
smile.gif
But it is dangerous generally to run at 70°C?
 
My first knee-jerk reaction is also....thermostat because of your statements of taking longer to warm up and running cooler.

I too use a 5-50. If anything, the higher viscosities allow for the engine to warm up quicker allowing the engine to reach normal operating temperature faster...another plus in my book. Check the thermostat.
 
Let's see now 70C, that's 158F.
gr_eek2.gif


That's running way too cold, even in Winter. You oil in never getting warm enough to get rid of condensation, etc.

I don't think it's an oil related issue. I'd put in a new factory spec. themostat. Lot's of parts stores want to sell you a colder one, but get the factory spec. heat range.

The thermostat in my truck failed in this manner.
 
Well, when the car was new (and used a 0W30 Castrol SLX oil), the engine coolant temperature was a steady 87°C!!! This is coolant temperature, not oil. At about 120,000km, I switched to a 10W40 oil and the coolant temperature went down to approximately 82°C and was 78°C with the last 5W40 I used. Now with this 5W50, the temperature is 70°C (in winter). Although I will for sure put a new thermostat at least as preventive maintenance, it seems that each time I went for a heavier grade (from 30 to 40 and then to 50), the coolant temperature deacreased. Moreover a 10°C decreased engine temperature is often advertised for synthetic oils and assuming my engine ran at "only" 87°C when new, I don't know if 70°C is really that cold. And really, I noticed this "problem" only after switching to that 5W50...so in the case I change the thermostat and the coolant temp remain as low as 70°C, would you recommend switching back to a 40 grade engine oil??? Is it possible that this 50 grade is too much and thus runs the engine too cold?

I must add that my engine is a 4cyl 2liters 16V normally aspirated with a aluminium block. I heard that aluminium blocks run cooler too...

[ January 06, 2005, 01:55 PM: Message edited by: kilou ]
 
My Corvette has an all aluminum engine, and I'm running Castrol SLX 0w30 and even in the coldest weather my coolant temp will still get up to 90C, even with a colder thermostat than most cars (the LS1 engine comes from the factory with a 177F thermostat instead of the typical 195 unit)
 
Sounds like the thermostat has been progressively sticking 'opener'.... and it diabolically coincides with the oil weight changes to mess with the owner's head... Break out the sludge detector.
 
quote:

Originally posted by NEPA_Z:
Sounds like the thermostat has been progressively sticking 'opener'.... and it diabolically coincides with the oil weight changes to mess with the owner's head... Break out the sludge detector.

Yep, an aluminum block will heat up much faster than cast iron and a thicker oil will also speed the process. Sticking open and getting progressively worse to full open would be a good guess.

Definitely fix the problem and change the oil at the same time. 70C is tooo cold. 87 is about right.

Your oil isn't getting hot enough to burn off condensation and contaminants or activate some heat activated additives at 70C.

Aluminum is a better conductor, hence it will heat up faster and will also dissapate more heat.

[ January 06, 2005, 03:03 PM: Message edited by: haley10 ]
 
quote:

Originally posted by kilou:

I also see that the mpg is lower than before as I burn 1liter/100km more than I did with the 5W40. I assume this is due to the elevated SAE 50 grade but is it normal that it does such a big difference?


Are you sure it burns almost 1 quart of oil in less than 70 miles in addition to what it burned before?
 
quote:

Originally posted by haley10:

quote:

Originally posted by NEPA_Z:
Sounds like the thermostat has been progressively sticking 'opener'.... and it diabolically coincides with the oil weight changes to mess with the owner's head... Break out the sludge detector.

Yep, an aluminum block will heat up much faster than cast iron and a thicker oil will also speed the process. Sticking open and getting progressively worse to full open would be a good guess.

Definitely fix the problem and change the oil at the same time. 70C is tooo cold. 87 is about right.

Your oil isn't getting hot enough to burn off condensation and contaminants or activate some heat activated additives at 70C.

Aluminum is a better conductor, hence it will heat up faster and will also dissapate more heat.


Going from SLX 0W-30 to a 5W-50 should have either no effect or warm the engine faster due to increased friction from the heavier viscosity, not the opposite.
 
quote:

Originally posted by benjamming:

[/qb]

Are you sure it burns almost 1 quart of oil in less than 70 miles in addition to what it burned before? [/QB][/QUOTE]

It burns 1 liter more gasoline, not oil. However it seems that oil consumption with this 5W50 is also bigger than it was with the 5W40. In 10,000km, I had no drop on the dipstick with 5W40 but with this 5W50, I need to add some oil now and then. Not a problem but strange since I would have thought the 50 weight would have stop oil consumption even more. Very strange no?

OK I'll buy a new thermostat and see if coolant temperature go up a little bit. In anycase, do you think there is any risk to run this 5W50 full synthetic oil type on my 240,000km engine or should I stick with a 5W40?
 
As oil consumption is higher with 50wt compared to 40wt oil (but I have absolutely no leak), is it possible that the oil pressure is too high and some oil passes through piston rings to be burnt in the combustion chamber? Is iz t actually possible to have too high oil pressure or will the relief valve in any case release excessive pressure so that no damage may occur from using an oil that is too thick?
 
Hypothetical answer to why it uses more oil with 50WT: Thicker oil is harder for the oil rings to scrape off the cylinder walls thus allowing more oil to enter the combustion chamber to be burned/blown out the exhaust? This could especialy be true if the engine didn't reach proper operating temperature. Burning more oil with a thicker viscosity IS contrary to conventional wisdom. Hope this is helpful... Rickey.
 
Those low temps sound more like oil temp readings, not coolant. If they truly are coolant temps., you need to heat things up.
 
The new thermostat braught my coolant temp back to normal. Thanks for the advice
smile.gif


The 5W50 oil I use is sold by Carrefour, a big supermarket company in France. This oil is badged as Carrefour but analysis have shown that it is in fact the old formula of Mobil1 5W50. It has shown great results in several tests when compared to other engine oils from reputable brands such as Castrol or Motul and as it's an old formula and it's rebadged and sold in supermarket, its price is incredibly low when compared to other engine oils. And it's fully synthetic of course.

This is why I went for that oil but now I wonder if the 50wt is not too much for my engine. Today I changed the 4 spark plugs and one was full of oil as if oil had passed through the thread. However the electrodes were clean. It was strange. Could this be due to an excessive oil pressure resulting from the use of that thick oil???? Unfortunately my car has no oil pressure gauge and checking oil pressure on mine is a bit complicated and better left to the dealer.

I really wonder if this 5W50 is good for my 240,000km engine. I used that oil thinking the added viscosity would be good for my """worn""" engine but maybe it's safer to stay with a 40wt oil. Are 5w50 oils really as safe as 5w40 oils when it comes to oil pressure, seals, rings etc? It seems that 50wt oils have much less car manufacturers specifications (MB229.1, BMW LongLife98 etc) than 5W40. Is there any risk to have excessive oil pressures with a 50wt oil?

[ January 07, 2005, 08:30 AM: Message edited by: kilou ]
 
quote:

Originally posted by RJCorazza:
Somewhat related to the topic... Who makes a 5w50 oil?

Pennzoil synthetic, Quaker State synthetic, Castrol Syntec, and Mobil 1 in Europe and Australia. Canadian Tire has a 5w50 synthetic too.
 
quote:

Originally posted by kilou:

Today I changed the 4 spark plugs and one was full of oil as if oil had passed through the thread. However the electrodes were clean. It was strange. Could this be due to an excessive oil pressure resulting from the use of that thick oil???? Unfortunately my car has no oil pressure gauge and checking oil pressure on mine is a bit complicated and better left to the dealer.


Chances are if you have an overhead cam engine where the sparkplugs pass through the valve cover then most likely the seal around the sparkplug hole is bad. I have a 2.0L Ford Zetec engine and my #1 sparkplug has oil on it's threads. And like you the "business end" of the plug is dry and fine. It's not bad enough for me to remove the valve cover and fix it a this time.

Whimsey
 
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