Engine runs cooler after oil change??

[Dustained]

The engine is a rebuilt Nissan GA16DE 1.6 L, DOHC. Everything inside is new (pistons, valves, etc.) and the block was remachined where it had to be.

For break in, I used some Motorcraft dino oil for 1000 kms (no oil consumption at all), and then changed it to Mobil 1 5w30 Synthetic. The car consumed a quart of Mobil 1 during the first 3000 kms after the change, and then nothing for the last 2000 kms. During all this time with Mobil 1, the normal operating temp was about 212 F, which I found a bit hot, because before rebuilding and with the dino oil after the rebuild, the temp always hovered around 194 F which is right the middle of the gauge.

Today I found Valvoline Synpower 10w30 at an excellent price at Autozone, and decided to buy it and change the oil. I know the Mobil 1 can last way more, but the temperatures here in this city of Mexico, never drop below 77 F, and the average is 99 to 104 F almost all year long, so I usually change the oil rather sooner.

Well, to my surprise, after changing the oil today, and today being a very hot day (102 F), the engine temp didn't even reach the once usual 194 F, it stayed at about 185 F. Is this even possible that an oil change/different oil could do this? Or am I missing something?

 

[Nyquist]

It sounds like your thermostat might be sticky.

 

[Dustained]

It could be, though it is also new, bought it during the engine rebuild. New radiator, water pump and hoses too.

I have always used M1 and I love it, but the price here is just too much now, 14 dollars a quart.

 

[901Memphis]

The heat is good for the oil, i wouldn't change it sooner in a hotter climate, it just means condensation isn't going to be as bad as the freezing parts of the world. Being hotter means the oil is thinner at startup too.

 

[Clubber_Lang]

If mobil 1 is that high locally, id order some through amazon, ebay ect. Buy it in bulk for a deal...

 

[Darwin1138]

Is your temperature dial accurate or is an "intelligent" type???, my VW used to mark 194F (90 C) over a wide range of temperatures, from 170F (75C) to 230 (110C). Most of the time the real temperature was around 220F (105C) but on the dial was 194F. But if the temperature went a little farther than 230 F then the dial started to show the real temperature.

Does your car has an oil cooler?
What coolant do you use before and after the rebuild?? If you use different types maybe the new coolant removed the old coating of rust inhibitors and that somehow block the thermostat??

 

[Dustained]

The dial is very accurate, at least to my knowledge. The car has no oil cooler, and I used the same coolant, Peak, before and after the rebuild.

The weird thing is that after the rebuild, during the break in with dyno oil, the car ran a bit cooler than with the M1.

I had a 1994 V6 Chrysler Town & Country for many years and more than 300,000 miles, and I always used M1 synthetic in it, I loved it. What I am thinking is that maybe M1 5W30 isn't right for this type of small (1.6 L) Nissan engine? Is it possible?

 

[tig1]

So you are saying that the differance in oil made a 18 F change in water temp?

 

[demarpaint]

Two things come to mind:

1. The thermostat is on its way out.
2. The engine is finally broken in.

 

[Dustained]

Originally Posted By: tig1
So you are saying that the differance in oil made a 18 F change in water temp?

I am ASKING.

 

[DoubleWasp]

Could it be that the first truly fresh oil change, after the break-in procedure was complete is why you are having lower temps?

I find it hard to believe a thermostat works properly before an oil change, malfunctions through an OCI, and then starts behaving with new oil around, but stranger stuff has happened, I guess.

 

[Dustained]

I think I may have found the culprit just now, though it still makes no sense to me: more than half a quart of extra oil that I just drained. Temps went back to the more usual 194 - 200 F, but certainly haven't reached the 212 F that was common with the Mobil 1.

 

[DoubleWasp]

Doesn't make sense to me, either, but, wow.

 

[Darwin1138]

I think that the oil quantity, viscosity or brand is unrelated to the water temperature, at least to a degree that you could measure in the instrument panel, just go for a drive looking at the temperature with a scan tool and you will see that the water temperature changes very rapidly over a wide range of temperatures depending on the speed, load, etc. If your thermostat and cap is OK, you are using coolant with the right density and the computer goes into closed loop operation when the engine is hot then you don't need to worry, although in this forum we worry too much.

5,000 km OCI is very short for Mobil 1 or VSP, at least go to 10,000 km. I just realized that you are in Mexico City like me, the land of the expensive oil, but there is still hope. At Sam's Club the 5qt jug of Mobil 1 costs 670 pesos (51 dollars) and in Costco the jug of Pennzoil Platinum costs 540 pesos (41 dollars).

 

[Dallas69]

Are you sure your oil level was full
If it was low your temp will be hotter