The vast majority of cars on the road today use electronic fuel injection. When your cars engine is cold, the computer tells the fuel injectors to stay open longer, allowing more fuel into the engine to help it run cold. As the engine warms up, the injectors let in less fuel and everything returns to normal, so to speak.

Richard Backus, editor of Gas Engine Magazine, notes that letting your car sit and idle is the slowest way to bring it up to operating temperature, because its generally sitting in your drive at just above idle speed. A cold engine emits a far higher percentage of unburned hydrocarbons than a warm engine. The average catalytic converter cant process 100 percent of unburned hydrocarbons even in the best of times, when exhaust temperatures are high. So the best bet is to start your car, let it run for 30 to 60 seconds to get all the fluids moving,then drive away gently. Maybe if itsbelow zero degrees outside, it would be a good idea to give the engine a bit longer before you drive off.

However, there is a time when a warmup might be in order, and that is when your spouse says its too cold to get into the car! At least wait until the temperature gauge gets off the peg.

A second legend is that you need to winterize your car, perhaps by changing to a different viscosity of oil. Have you ever wondered why motor oil sales in various do-it-yourself outlets occur in April and October? Thats a throwback to the days when oils usually came as monogrades. SAE 30 was the recommended choice for summer driving and something lighter, perhaps SAE 20 or SAE 10W, were suggested for winter. Of course the latter depended on whether you were in Minneapolis or Los Angeles. Even though multigrade oils were the choice when I went to work at Pennzoil in 1980, the seasonal sales plan still existed.

Todays recommendations are based on the owners manual, which usually points to a specific viscosity grade year around. For my 2008 Quest, its SAE 5W-30. I live in Arizona, where the summers are hot (an understatement) and the winters are surprisingly cool (could be 20s in the morning and 50s in the afternoon). Its certainly not a myth to say, read your owners manual!

While were on the subject of SAE grades, another legend is that the W in SAE XW-XX stands for weight. No, it doesnt; it stands for winter. That should be obvious when you realize that the first number followed by the W tells you the minimum temperature at which the oil will pump and flow.

Another point about SAE grades is how they should be written. According to SAE J300, the standard that defines the various grades, the proper way to designate is SAE XW-XX. The designation SAE must be part of the labeling. Simply stating the range is not correct. Neither is reporting a series of grades such as SAE 0W-20, 5W-30, 10W-40. Only the lowest winter grade met and the highest summer grade should be on the bottle. So for my example, the appropriate grade would be SAE 0W-40. Now that Ive got that off my chest, lets move on.

The 3,000-mile and three-month oil change did have a place in the past. It was a part of OEM recommendations in the 70s, but as engines grew more sophisticated, it was no longer necessary. Oil quality improved to the point where longer drain intervals were acceptable. The introduction of the oil life monitoring system was a vast improvement in determining oil change intervals and should be followed. Remember, the OLM system takes the range of engine oil temperatures and compares them to the number of revolutions of the crankshaft. Based on lots of field test data, an algorithm determines when the oil should be changed.

Whats an algorithm? The definition is a self-contained, step-by-step set of operations to be performed. Algorithms exist that perform calculation, data processing and automated reasoning. In this case, the temperature range is compared to data from field testing and associated with oil condition. The light comes on when the oil life is similar to oils that had run their course in the field test.

There are a couple of urban legends associated with synthetic engine oils. The first one is that synthetics cause oil leaks. While that may be a possibility with pure PAO, which could dry and shrink seals, the actual formulations of PAO based oils usually contain a small percentage of an ester synthetic. The ester will swell seals as well as solubilizing additive systems, so put that one to bed.

Another legend is that if you start using a synthetic you must forever continue to use synthetic. I frankly dont know where this one started, but there is no reason you cannot change from one synthetic to another or to a mineral oil based product. The important things to consider are what your owners manual says (there it is again) about viscosity grade and API category.

Speaking of engine oils in general, there are some legends about them as well. The first one is that switching brands is bad. As I said about synthetics, the keys are viscosity and API category. Another one is that higher viscosity engine oils are better for smaller, hotter running engines. This one is a twofer. First, smaller engines dont run hotter; they run at the optimum temperature for their design. Second, higher viscosity engine oils arent a good idea for smaller engines. They need the same viscosity oils as other engines. Check the owners manual (getting repetitive).

Heres one to watch out for: Racing oils are always better. Sorry folks, thats a negative. In fact, racing oils are very specialized and vary from one type of racing to another. For instance, top fueled dragsters run on a special formulation, which includes antiwear additives and an emulsifier to soak up the nitrobenzene that collects in the crankcase due to blow-by. Its not really suitable for much of anything else. Another one is open-wheeled racing (Indy cars), which use an oil that has extra antiwear and antioxidants but not nearly as much detergency or dispersancy as standard oil.

The last set of legends I want to address are about the oil itself. There is a persistent legend that dark oil should be changed. Actually, dark oil is not necessarily due for a change since it turns dark pretty quickly. In fact, the color is an indication that the oil is doing its job of collecting sludge and varnish. If you want to know when to change the oil, check the viscosity. When it gets very thick its time to change.

When I was at Pennzoil, there was a legend that Pennzoil or any other Penn Grade product actually caused sludge. I can assure you that doesnt happen. In fact, one of the field technical services managers even told several customers that if that were true, there would be one out of five cars on the side of the road! That was the market share of Pennzoil (20 percent) at the time.

Well, enough of these stories. Suffice to say there are many more out there. I was looking on the Internet for some additional items and stopped counting after I hit 20 or so. I decided to save them for another time.

Just remember this: Oils that have API certification (either the donut or the starburst) and the proper viscosity will serve you well. Need I say it again? Be sure to check the owners manual before servicing your customers.

Industry consultant Steve Swedberg has over 40 years experience in lubricants, most notably with Pennzoil and Chevron Oronite. He is a longtime member of the American Chemical Society and SAE International, where he was chairman of Technical Committee 1 on automotive engine oils. He can be reached at steveswedberg@cox.net.