The percentage of Oxygen at any altitude and temp (in the Air) is always the same.
It is the partial pressure of Oxygen and the other gasses in the Air that is different at different altitudes and temps.

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84 300D, 82 Volvo 244Gl Diesel

Ive always found cars can be like people in the fact they have their good days and their bad days. Sometimes I'm driving and I can just feel the car is running poorer than usual. I might feel like it has a grumpy idle or its making a noise a little louder than usual. Then some days its running like a top and I'm like "damn this car is running great today!"

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual

That is what I think... was wondering if everyone was going to let Brian get away with that ' yes '... LOL

For gas engines when the air temperature is lower more can fit into the same bore .... thus more power is available since the ratio of air to fuel is assumed to be the same...you are both able to and do burn more fuel per revolution.

On our diesels... unless one has a ' mass sensor' to change the amount of fuel ifuel injected... I do not believe more power is made at lower ambient air temperature... I do think our machines may have a pressure sensor which will do some compensating for altitude... but do not think that is related directly to temperature ( and thus density ) of the air.
I am referring to NA engines.... I do not know about the others....

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/diesel-discussion/10414-help-i-need-check-stretch.html

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html