Auto and Truck Repair and Advice
Serving the Gainesville and Hawthorne Florida Area
What Type of Oil Should You Use?
OIL VISCOSITY
An oil's viscosity is just how thick it is. Viscosity is measured by an oil's "weight" Way back when all cars used 30 wt (weight) oil. This is a single grade oil: its actual viscosity varies with temperature. single grade oil gets thinner when hot and thicker when cold. Multigrade oils have labels like "10w-40" or "20w-50". Their thickness changes with temperature also, but they change the opposite way from single grade oils. A 10w-40 motor oil behaves like a 10 wt oil when cold and behaves like a 40 wt oil when hot.
Generally a thicker oil will withstand more abuse, however thick oils can take longer to reach engine parts when the engine is started. In cold climates a thinner oil (lower "wt" number) is often used to compensate for this. Engine startup is when most engine wear occurs: it runs for few seconds without oil pressure every time you start it.
Manufacturers are using thinner and thinner oils in cars. (5w-30 wt is recommended for many new cars.) This is primarily for fuel efficiency. In Florida I've never seen a car have problems from using a thicker oil than this, but then again I haven't seen any of the new ones burn up engines from these thinner oils. I have seen higher mileage engines consume more oil of the lower viscosity types: if your engine uses more than 1 qt every 1000 miles you might use a higher viscosity than recommended by the manufacturer. Another reason to go with a slightly higher viscosity would be if you anticipate driving in extreme high temperatures. Otherwise, I'd stick with whatever grade the manufacturer recommends.
What about those additives?
There is a bewildering array of oil additives on the market today. They make claims of increased fuel economy and engine wear prevention. Some promise to be an engine overhaul in a can!
Although not all additives are "snake oil", I personally don't recommend them. I say use the oil grade and viscosity (weight) recommended by the vehicle manufacturer. Use the same type of oil all the time if possible. Use a reputable national name brand (any of the major oil companies oils, or independents like Valvoline, Castrol, Kendall, Pennzoil, to name a few.) Stay away from weird or look-alike brands.
Change the oil every 3000-5000 miles (depending on how rough your driving conditions are) or every 6 months. (Cars that sit condense nasty acids in the pan, so do the change on a time basis even if you haven't done the miles)
Additives fall into 3 categories:
1) Additives that thicken the oil
The oldest and best known of these is STP. I know people who swear by it, and I'm not going to argue with them. These increase viscosity, and this means more oil will stay on the engine parts longer. This could help in startup (see hydrostatic bearings article).
How it could hurt:
Modern engines have a lot tighter tolerances than older motors. In extremely cold weather, the thickened oil could take too long to get to certain parts of the motor. The 305 Chevy motor was burning up front camshaft bearings up north a few years back. Turns out too thick oil was the cause.
How it could help:
In a high mileage motor, it might just help a bit. Also, in extreme hot weather or racing applications, the thicker stuff might help.
2) Additives that thin the oil
These usually claim to clean the motor, free up lifters, etc. Once again, on a normally functioning motor this shouldn't be needed. Any good motor oil has detergents (cleaners) in their oil. Regular changes will keep your motor nice and clean.
How it could hurt:
Thinning the oil means it won't stay on the engine parts as long when you shut off the engine. (see hydrostatic bearings article). Under extreme loads, the thin oil will break down quicker. Also, the additive may not be compatable with the additives already in the oil. Also, if it did break loose a bunch of sludge, the sludge could clog oil return holes or the oil pickup screen in the bottom of the pan. If this screen clogs, you lose oil pressure, and can destroy your motor.
How it might help:
If you've got a really sludged-up engine, one of these might free your stuck lifters. A lot of these are just kerosene or transmission fluid. I'd recommend a quart of automatic transmission fluid to replace 1 quart of oil on a 5 quart change to free lifters. It will probably work as well as the additives, and is much cheaper. Don't run it forever: just a few hundred miles, then change the oil.
Additives with particles of teflon or zinc
The best known of these is Slick 50. Although great claims have been made for such stuff, I still say stick with just oil. I have yet to see proof that the teflon or zinc actually stick to the engine parts, and it would seem that would be an easy enough thing to have verified by an independent lab. Plus, how do these "micro-particles" keep from gathering in the oil passages and filter?
How it might hurt:
Clogged filters and oil passages with the teflon stuff, plus additive incompatability with the zinc compound stuff.
How it might help:
Once again, it might help a high mileage motor. There are a lot of folks who swear by the stuff, but this could be a "placebo effect!"
How about synthetics?
Synthetics actually are pretty good. You HAVE to use them in Alaska: regular oil turns to jello!
A couple of problems: read the label: many "synthetics" are part synthetic oil, part "carrier oil" whatever that is. The makers don't elaborate, but I assume it's just regular oil. Often the percentage of carrier oil is like the percentage of "inert ingredients" on a can of insecticide! You're getting 5% or so of synthetic.
Synthetic problems
The only negative (besides price) on the synthetics is oil seals. Although the makers claim to have eliminated this problem, I've found starting to use synthetic oil in anything but a new or newly rebuilt engine is asking for all kinds of oil leaks.
These leaks won't go away by switching back to regular oil: the seals are trashed. So if your vehicle has more than 25000 or so miles, or more than a year or so old, I'd recommend staying away from the synthetics.
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We also serve the surrounding communities of Alachua, High Springs, Hawthorne, and Newberry!
Thank you for visiting the ECONOMECHANIX WEB SITE. Please feel free to comment. We also serve the surrounding communities of Alachua, High Springs, Hawthorne, and Newberry! Gainesville has been my home since 1974, and I've loved Gvl and the Gators since I came here in the fall of 1974 to attend the University of Florida. I loved it so much I stayed and opened my car repair business. Originally it was out of the back of a 1963 Chevrolet wagon, but in 1977 a fellow mechanic and I opened an auto repair shop with actual walls, etc. I stayed in the same location for 26 years, and recently moved my operation to property I bought 15 miles east of Gainesville. I am doing most all the repairs myself now, having reduced my overhead from $1500 per month to practically nothing. I do work by appointment only. I mostly work only on my established customers cars, but I will occasionally take on new clients. E-mail me and I will either make arrangements to look at your car, or I will recommend you to someone who will.
George G. Scott, Jr.