Why You Should Read Your Car's Owners Manual Cover-To-Cover

Phil Ramsey

Automotive dealers claim the most unused part of any new car they sell is the little book in the glove compartment - the owners manual. Have you ever read yours, cover to cover, or even thumbed through any of the pages? There is a wealth of information in that book. Granted, the prose may be boring at times, but the information is valuable - you should read it!

Published in a recent issue of Car Craft magazine was an article about Valvoline’s new 0W-30 motor oil. That’s right, 0W-30 oil, zero viscosity! The article discussed the pros and cons of this product, specifically a gain of several horsepower at operating temperatures.

It made me think of the local gearheads who will try to squeeze a few more horsepower out of their cars by using this new product. The implication from the auto and truck magazines I’ve read, and TV shows I’ve watched, is that a good rate of return for dollars per horsepower is about $40/hp. Free horsepower is a powerful temptation, but how do you know if it’s right for you?

Car Owners Manual

The past few years I have served as an expert witness for several attorneys. Many times I have been called to a holding yard for vehicles involved in criminal cases. When investigating the cause of such accidents, the first step is to sample all the fluids in the vehicle. Motor oil, transmission fluid, brake fluid, power steering and various greases are all bottled and sent to the lab for examination. Technicians look for cross-contamination or just outright errors of service personnel using the wrong fluids. In most of the cases where cross-contamination was the culprit, the accident could have been avoided had the owners manual been consulted.

One of my most likeable customers is a young oyster fisherman. He recently brought his wife’s 1999 Chevy Suburban in for brake repair. The bill came to more than $1,300, far more than the father-of-eight could afford at the moment. Why did the seemingly basic brake repair cost so much? Although he won’t admit it, hydraulic fluid was somehow introduced into his 4-wheel antilock brake system.

The rubber components in the system had swollen and lost their shape. The front calipers locked up, dragging the disc pads on the rotor and grinding them to dust. The proportional control valve in the antilock computer malfunctioned, allowing no rear brake engagement. He therefore had no rear brakes, and was within hours of having no brakes at all.

Hydraulic brakes should have hydraulic fluid added, right? Wrong in this case. All parts in this system with rubber components, such as calipers, hoses, seals and O-rings had to be replaced. This young man didn’t know his owners manual recommended a specific type of brake fluid, not hydraulic fluid. Fortunately no accident occurred.

There are several types of automatic transmission fluids. Are you sure of the types of fluids which belong in your vehicle? I am convinced that several of the prematurely burned-up transmissions I’ve seen in my shop got that way by indiscriminate use of automatic transmission fluids (ATF). At one time it was easy to memorize all of the applications for ATF.

We now have so many different manufacturers, and service guidelines from them, that I no longer trust myself. I always check my Alldata® database or the owners manual of the car being serviced.

Do you use green or red antifreeze in your car? New requirements, based on aluminum components, have introduced another antifreeze into the market place. Which one do you use? Check your owners manual to see which is recommended.

In previous columns I have discussed motor oils, tire pressure, air conditioning oils, PCV valves and multiple viscosity oils. All of these subjects are covered in the manual. The owners manual discusses these items plus dozens of helpful hints to extend the life of your drive-train, paint, interior, vision and safety equipment. It also provides suggested maintenance schedules.

A spot check in my shop did not find a single late-model owners manual allowing use of oil with zero SAE viscosity grades, such as 0W-30. I know of a few vehicles that accept 5W-20, but as I’ve written before, I feel this is for the sake of elevating the Corporate Average Fuel Economy (CAFE), not for any other benefit.

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