1998 Ford Mustang Gt Motion
KJ Jones Brand Manager, 5.0 Mustang & Super Fords
April 29, 2014

Trading Places

Q: I have a '98 Mustang V-6, but I'm going to put a 351W in it. Why do I have to change the K-member in order to put the pushrod engine in the car? I have a friend who has a '94 Mustang with a swapped V-8, but he didn't have to change the K-member. What's the difference in the '94 and '98 K-members? I'd rather not change them if it isn't necessary.

Al Perkins
Hampton, VA

A: The K-member swap is necessary because the engine mounts for your '98's 3.8-liter V-6 engine will not support installing the 351W as a straightforward swap. You definitely will experience major problems with aligning the engine and transmission if you try and go forward with the effort. The V-6 or V-8-powered '94-'95 Mustang's engine cradle or a tubular, aftermarket K-member are the parts needed for the project (and there still may be some minor fabrication required).

Before you get started, there is one thing to consider—the stock engine mounts on your V-6 car definitely will support a 4.6-liter V-8 install.

Slick Benefits

Q: I'm curious about motor oils and their influence on horsepower/longevity. I've used synthetic oil (Mobil 1) for many years now. My '88 Mustang GT 5.0 had over 400,000 miles when I sold it. It still ran fantastic, didn't smoke, and started great.

I'm once again using Mobil 1, this time in my '12 Mustang GT 5.0. Since I started using the Mobil 1, my stocker appears to rev up quicker and the car seems to be peppier. Passing is a real treat. What's the true story on the effect of motor oils on engine performance, horsepower, and long life?

Via email

A: Questions like yours make us glad to be associated with people like Lake Speed Jr., who is a certified lubrication specialist. Bottom line? The man knows engine oil. here's what he told us in response to your great question:

"Here is the straight truth. The synthetic base oil used to make synthetic motors oils like Mobil 1, Driven, Royal Purple, or Amsoil have three specific benefits over petroleum-base oils used to make conventional motor oils: lower traction coefficient, higher viscosity index, and greater specific heat capacity. Before you Google those words to see what the heck I just said, read these brief explanations and how those three properties provide better engine performance, horsepower, and longer life.

First, lower traction coefficient: Everybody loves extra horsepower, and lower traction coefficient is a fancy way of saying less drag. A motor oil that has less drag allows the engine to accelerate faster and make more horsepower. This benefit also can be seen in improved fuel economy. Synthetic base oils offer a lower traction coefficient compared to conventional base oils, so synthetic oils provide more horsepower than conventional oils. That is why Pro-Stock drag teams use lightweight, synthetic oils: more power and faster acceleration due to lower traction coefficient.

Second, higher viscosity index: All oils have something in common with pancake syrup—they get thinner as they get hotter. Just like syrup is thick when you take it out of the fridge, motor oil is thick when it is cold, but motor oil thins out just like syrup does when it gets hot. However, not all oils thin out at the same rate. The rate at which oil thins out with increasing temperature is called Viscosity Index. The greater the Viscosity Index, the less the oil thins out. I know that sounds backward, but that is the system. A high-viscosity-index oil resists thinning out better than a low-viscosity-index oil, and as a result, the higher viscosity-index oil will have more viscosity at higher temperature. More viscosity at high temperature means better high-temperature protection.

Synthetic base oils have a higher viscosity index than conventional oils, so synthetic oils offer better high-temperature protection. This is why every NASCAR team uses a synthetic-based motor oil. In fact, Driven Racing Oil got started making specialty synthetic motor oils for the top NASCAR teams. To race at wide open throttle for 500 miles, you better have an oil with a high viscosity index. If you plan on winning, you better have a low traction coefficient, so Driven specialized in making high-viscosity-index, low-traction-coefficient motor oils. In fact, making a 5W-50 motor oil like Ford calls for in some of the new Coyote engines requires a high-viscosity-index synthetic formula. Driven just released FR50, a synthetic, high-viscosity-index, low-traction-oefficient 5W-50 based on its NASCAR-proven formulas.

Last but not least, greater specific heat capacity: Oils do more than just lubricate—motor oils provide as much as 40 percent of the cooling for your engine. The specific heat capacity is a measurement of the ability of the oil to absorb heat. The higher the specific heat capacity of the base oil, the more heat the oil can absorb without ‘overheating' the oil. Accordingly, the higher the specific heat capacity, the better the oil is at cooling the critical components in the engine. A synthetic oil has a greater specific heat capacity than conventional oil, so a synthetic oil provides better cooling. Keeping items like pistons and valvesprings cool extends the life of those components. As a result, synthetic motor oils help extend the life of your engine.

All in all, synthetic oils provide better lubricant performance than conventional oils for specific and scientific reasons. While synthetic oils do cost more per quart, they obviously more than pay for themselves in extended engine life and increased performance."

Virgin of the Month

Size 'em up

Q: I just got a new '14 GT. The car is awesome, and I want to get it to the track once the weather thaws out. The car came with the bigger Brembo front brakes, and I'm wondering what size rear wheels I can use for the drag test. I've seen other Coyote Mustangs with 15s and 16s on them, but is there a specific combo?

Kenny Allison
Via the Internet

A: Based on S197s that we've seen at the track, especially in the NMRA's Super 'Stang class, 15-inch rear wheels appear to be the most widely used size. The 15x8-inch is the hot ticket, with 5.25-inch backspacing. This size supports a 26x10x15-inch slick with no clearance issues. This is important especially with the rear sway bar, which must be relocated if you try and use a 15x10-inch Weld RT-S (or bigger diameter) wheel.