Pat’s Perspective – Oil

Every week I get oil questions like, the guy who changes my oil says I should be using thicker oil in my car. I trust him, but I don’t know about this advice. What should I do? It seems far too many people who change oil know more than the engineers who design engines. These morons keep telling drivers to use thicker oil for better protection. But, better protection doesn’t come from thicker or thinner oil. It comes from the right oil the engine was designed to use.

Don’t be a moron and do it because two morons don’t make a genius. Changing oil, no matter how many times anyone does it, won’t magically morph them from oil changer to oil engineer or chemist. Nor will changing oil teach anyone the steps used in a refinery to change crude oil or synthetics into something that can protect the parts inside your engine. This means protection during cold starts, blazing hot days in traffic, and every situation in between. Sadly, changing oil will not make a tech into a metallurgist that can study the amount of expansion of engine parts as it heats up. Nope, changing oil or even repairing engines won’t give anyone the knowledge necessary to make recommendations to switch from the oil recommended by the manufacturer to something not recommended by the manufacturer.

The primary job of oil in an engine is to keep moving parts from touching one another. This is done by means of a thin film of oil in gaps between parts that keep them from touching. But, heres the rub, as engines have become more precise due to sophisticated computer controlled machining….the space or gap for this film of oil has become smaller.This means these engines need thinner oil to pass through those smaller gaps and still provide the film of oil necessary to keep parts from touching. Also, nearly all engines these days have variable valve timing which works off oil pressure. Changing to a thicker oil changes the pressure needed to move oil through the engine. That increase in oil pressure can confuse the car’s computer…which controls the variable valve timing leading to lowered performance, lower gas mileage, or in some cases even a check engine light. Bottom line, changing oil or repairing cars does not give anyone (myself included) the knowledge to determine if a change in oil thickness will be good/bad/indifferent for an engine.

In other words, don’t reinvent the wheel. The manufacturer has spent millions in testing and engineering to determine the right oil for your car. Did the person changing your oil spend millions of dollars to develop their suggestion or is it just mental fantasy or outdated wacko bull? Unless the vehicle manufacturer issues a bulletin telling you to do something different, always use the oil recommended in your owner’s manual. Very few people are smarter than the engineers who designed the engine and typically they won’t be changing your oil.

Drive Gently
-Pat Goss

Pat’s Perspective – C-P-O’s

I think there may be more fake stories about cars then politics. Myths like, buy a used car and all you’re getting is someone else’s problems. That’s pure garbage. I don’t know if that ever was true, but I do know it isn’t true today. Sure, some used cars are dogs, but many late model used cars are creampuffs due to leasing.

Lots of Drivers lease their new cars to get a lower payment or tax advantage. The typical lease is three years and comes with very strict requirements for maintenance and appearance care. When these cars are turned back in at the end of the lease, the great ones usually become certified pre-owned or C-P-O cars. CPO cars are generally good deals, because they’re thoroughly checked out. Someone else has also paid the big, or in many cases, huge initial depreciation hit for you! Plus, CPO’s have a warranty that may be better than the new car warranty. You also still save some money!

On a three year old luxury or near-luxury CPO, you might save twenty to forty percent or more compared to new. You can choose between paying less money or the same money and step up to a higher level of car. Of course, always get a Carfax vehicle history report, have any car checked from bumper to bumper by a qualified technician before you buy. But do it right, and you will be driving a car where someone else paid your initial depreciation for you. Now that’s smart!

-Pat Goss

Will changing the air intake and exhaust help the performance and
mileage or just make it sound good? Specifically I was wondering if the cost would be paid back in a year or two by mileage improvement?
Paul Read More

Sure do! There are several possibilities but the two most common that we experience here in the shop are control module and air blend door motor. The system uses various sensors outside and inside the car to tell the module what commands to send out to blend motors that control how hot or cold each side of the car will be.

As the sensors send signals the module which is actually a small computer analyzes them and decides based on internal programming how to set the air blend doors. Air blend doors control how much air passes through the heater core and how much air passes through the AC evaporator. Of course more air through the heater core means hotter air coming into the car and more air through the evaporator means colder air. Read More

Well, I have another puzzling issue with a 1992 Corvette base coupe with 80,000 miles.

The LCD display for the speedometer started to fade a few years ago and although it still displayed the mph, it was getting hard to see. I procured a replacement LCD display and carefully installed it. Afterwards, the LCD was bright and clear for a couple of months without issue. Read More

Question: I want to replace the front coil springs and understand there are no factory replacements available, only after market springs. I also understand that it’s a real crap shoot on how those aftermarket springs will make the car sit. Ride height is critical to me as I want the car to sit dead level and was told things like engine size, options etc… can all affect ride height with the aftermarket springs. Do you know of an aftermarket spring that will give as close as possible correct ride height? 

Guess what? You’re in luck because it isn’t that difficult. Simply go to one of the major Corvette aftermarket suppliers and look up springs for your car. You should find 2 listings: one for big block and one for small block. Buy your small block springs and install them. The front end will likely sit higher for a few weeks until the sprigs break-in and settle to a normal ride height. Once they have settled don’t be surprised if the front is still higher than the back. After all you have two new front springs and a used saggy rear spring.

At this point you can do one of two things: install a new rear spring and adjustable spring hanger bolts or install adjustable rear spring hanger bolts and adjust the car until it’s level. Due to normal variances in springs in general this is the best way we have found in the shop to precisely level a Corvette. Actually back when your car was new because GM was notoriously bad about the quality of their OEM springs we often had to level brand new or nearly new Vettes.

Q. My neighbor tells me that her 1996 Vette’s a/c does not work after starting the vehicle. After driving for awhile the a/c starts working, what could be the problem. Thanks. B.

Pat says. Begin by checking the level of refrigerant in the AC system. When refrigerant is borderline low it may not have enough pressure when cold to trip the pressure switch to allow the system to work. Then as the car is driven engine heat warms the refrigerant, the refrigerant expands and the pressure increases. Now with warmer refrigerant there is enough pressure to close the low pressure switch and on comes the AC.

Actually no! The major difference between cylinder heads for engines designed for leaded and no lead fuel is valve seat hardness. To make a proper no-lead fuel engine the valve seats must be hardened to resist recession. This did not universally happen at GM until 1973.

If you think about it valve seats take a real beating in all engines. As the valves are pulled shut by the valve springs they bang against the valve seats. To visualize this, strike the anvil portion of your bench vise with a steel hammer. You will hear a distinct metal on metal ringing sound as the hammer hits the vise and you will see a tiny dent in the anvil where the hammer struck. For comparison take an old lead wheel weight and position it on top of the spot where you hit your vise and hit the lead weight with the same hammer. This time you’ll hear a dull thud rather than a metal on metal clang. This time there will be no dent in the vise either. Read More

Smooth Ride

Complaints about cars shaking at speed have increased ten- fold in the last few years mostly due to new suspension designs. Today tires wheels and suspensions are designed to work as an integrated system. But this only works when tire and wheel assemblies are perfectly round and roll smoothly. So tires must be properly balanced and must not have excessive rolling resistance. If a tire has a hard spot in its tread it will never roll smoothly no matter how many times it’s balanced.

The secret to making a tire roll smoothly is offsetting the imperfections in the tire to the imperfections in the wheel using a process called match mounting. Never heard of it? Neither have many technicians. Match mounting involves rotating the tire on the wheel so the high or heavy spot of the tire is matched to the low or light spot of the wheel. This requires a balancing machine that measures these factors and checks for stiff spots in the tire’s tread. The machine tells the technician how to rotate the tire around the wheel for smoothest ride.

So before spending money on an old-school run-of- the-mill wheel-balancing job remember you’ll get a smoother ride if you seek out a high-tech hunter road force balancer.

Stay tuned we’ll be right back.

Clean Cars

You’ll feel better about driving a clean car plus good looking cars are always worth more money. Part of what makes a car feel old is the general layer of crud that builds up over time. Let the car go too long and it may be nearly impossible to make it look good again. It’s fun to watch someone as they see their cruddy car for the first time after it has been detailed. Some drivers don’t even recognize their own car because it looks so different cleaned up. Read More

Be Seen

As daylight gets shorter it’s more important that your car can be seen so all its lights must work properly. Checking takes two people and some distance. Stand back from the car about fifty feet while a helper operates the lights. The distance is so you can see differences in brightness that isn’t visible up close. If one light is less bright than its companion check the bulb to make sure it’s the proper type. Many bulbs will physically interchange but the watts of light they produce is different. Read More