frigid-87 octane

today after 2 days of frigid weather my new(april 04)325i was repeatedlycranking hard and when started ran very very rough for awhile.service engine light momentarily came on.called dealer when I got to work to ask if I did something very wrong.he said in this winter use 87 octane.the chemicals for high test result in tough ignition.so I added dry gas and filled with 87.have you heard of this before.?
amazingly the windows worked although the radio steering controls and radio/time display froze up as usual when this cold outside.

Using premium in the winter may make your car a little harder to start because it doesn't vaporize as quickly in cold weather as lower octane (regular) gas.

Premium fuel has inhibitors which restrict pre-ignition under heavy-throttle conditions, but it can be a (slight)disadvantage on cold starts.... one reason to keep your car in a good state of tune. Someone passed along an interesting tip....in *really* cold weather, turn your headlights on for about a minute, shut them off, then start the engine. The theory behind this is that it supposedly gets the electrons flowing inside the battery, and lessens the strain upon starting. Any of you electrical wizards care to validate or dispute this claim?

Regards,
Bob

I was under the impression (perhaps wronfully so) that the formula of gasoline was altered between the seasons to account for the temperature changes.

Fast Bob, I've never heard of that trick before.

Originally Posted by Fast Bob

Premium fuel has inhibitors which restrict pre-ignition under heavy-throttle conditions, but it can be a (slight)disadvantage on cold starts.... one reason to keep your car in a good state of tune. Someone passed along an interesting tip....in *really* cold weather, turn your headlights on for about a minute, shut them off, then start the engine. The theory behind this is that it supposedly gets the electrons flowing inside the battery, and lessens the strain upon starting. Any of you electrical wizards care to validate or dispute this claim?

Regards,
Bob

Seemed to work this morning. I accidently left the dome light on in my truck overnight, and it actually seemed to start a little faster than normal. Of course, it was a bit warmer than the last few days too. I supposed the theory would be based on gently warming the battery with a low current draw before hitting with the higher draw of the starter. Personally, I'd like to see Mythbusters handle this one.

Originally Posted by Fast Bob

Premium fuel has inhibitors which restrict pre-ignition under heavy-throttle conditions, but it can be a (slight)disadvantage on cold starts.... one reason to keep your car in a good state of tune. Someone passed along an interesting tip....in *really* cold weather, turn your headlights on for about a minute, shut them off, then start the engine. The theory behind this is that it supposedly gets the electrons flowing inside the battery, and lessens the strain upon starting. Any of you electrical wizards care to validate or dispute this claim?

Regards,
Bob

Electronics man here....the logic behind that is that the current a battery (any battery) can supply is dependent on its temperature. If you've ever tried to run some portable item (cell phone, walkman, iPod, etc) when it's cold out, you may notice the battery lasts a lot less time. So having the lights on will get the battery started producing current, which also serves to heat it up a bit. That way, when it comes time for some serious current to the starter, the battery is more ready to supply it....

They need a smiley with a chalkboard and a tweed jacket.