While there are a number of posts on this forum dealing with the hot weather I'm getting ready for the inevitable - winter in New England.

I've installed oil pan heaters on my last four vehicles and they seem to really make a difference with warm ups/fuel economy. The NAH presented a problem in that it doesn't have a flat smooth surface on the bottom of the oil pan - it has sort of a ribbed surface. I looked around and purchased a 125W stick on oil pan heater from Wolverine that's 6 in x 1 & 1/2 in and will just fit on the front edge of the oil pan.

After plugging it in for about two hours the end of the dipstick feels nice and warm. I've noticed that when I tested it on a cold engine that the blue temperature light goes out sooner - about 1/2 a mile instead of about 3/4 - but the outside temp was only about 45 degrees. It doesn't heat the coolant but it still seems to speed up the warm up plus I'd rather have warm oil instead of warm coolant to help the engine wear less.

http://www.wolverineheater.com/

Another possibility is to use an engine block heater - if the Altima provides for one.

A lot of Prius owners a using engine block heaters to do just that. Keep the car warm to improve fuel economy in cold weather.

But Toyota USA didn't provide much help. The Prius owners had to check with Canada to find out that the car did have provisions for an engine block heater. They then were able to order the heaters. (The heaters are made and shipped from Canada!)

And to top it off, the service manual doesn't show where the heater goes! People had to figure that one out too!