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Why Are Some Cars More Costly To Maintain Than Others?
I admit to being stuck in the 1980's. I like the music. When my wife and I went to a 80's retro party I didn't need a costume - I just went into my closet and dusted off some old clothes. I have been driving 80's cars for the last 20 years; mostly Mercedes and Porsches, but lately Jaguars. These are the last cars where the enthusiastic owner can do his or her own maintenance without proprietary diagnostics and a degree in computer science. Spending quite a bit of time under the hoods (bonnets) of these cars, I've come to appreciate the differences.
I've written in this column that I consider the W126 Mercedes-Benz S Class (1979-1991) to be the best car ever made. I still think that if the criteria are build quality, longevity, structure and ease of maintenance. The car was praised in the late 1970's when it was introduced for its luxury and efficiency. In the later part of the vehicles life it was criticized for noise and suspension harshness compared to newer offerings which had computer designed multi-link suspensions that did a better job of insulating the cabin from NVH. I have to admit it isn't a particularly quiet car and it isn't particularly luxurious. It does make an excellent useable classic car though, and it has served our family well for 10 years. With only 66,000 miles in the first 33 years, the car will outlast me.
I think that the Jaguar is a better engineered car which may surprise people, especially those who have memorized all the 'Lucas Prince of Darkness' jokes. The thing about the Jaguar XJ series, for instance, is that they were designed with different objectives in mind - namely refinement and effortless performance. There is no doubt that they achieved these objectives admirably. What is not generally appreciated is that the engineering solutions required to meet these objectives result in a car that is more time consuming to maintain. Generally speaking this is not a fault of the car, but a tradeoff for the extremely low levels of NVH.
V8 vs. V12
When the metal parts of an internal combustion engine expand and contract with each heat cycle the gaskets between the parts will eventually fail and start to leak. Different engines may be prone to leak different things from different places, but they will all start leaking - usually before they are 10 years old. Gaskets are not expensive, but the labour can be, depending on how hard the access is.
I have to replace the valve cover gaskets on both the Mercedes W126 and the Jaguar XJS. I can probably do the Mercedes in 1 hour myself. My Jag mechanic says he could replace the gaskets on the XJS in 12 hours - and he's done it 500 times. Triple that time for me trying it for the first time, and that's if I don't wreck anything in the process. Reading this you might think the British don't care about maintenance or can't design a proper engine - but that isn't the case.
The configuration of a 4-stroke combustion engine starts with balancing the primary and secondary forces of the crankshaft and firing order of the pistons. A V8 configuration will normally have a 90 degree 'V' for the optimum smoothness, without the use of a heavy flywheel. This is a fairly wide angle which gives enough space in the centre of the V for the intake manifold and the air/fuel injection system. If you have all the intake parts in the centre of the V, the valve covers are exposed and you can change the gaskets easily.
Let's say you want a smoother engine that can provide high output - then you want a V12. It is inherently perfectly balanced, as is a straight 6. The Jaguar V12 is 'over-square' meaning the bore is wider than the stroke. This gives lots of room for big valves, and lower piston speeds which means less wear. The lighter reciprocating mass of the pistons and valves allows for higher RPM and higher specific output. From a performance and smoothness perspective it is the perfect layout - which explains why so many of the most successful racing and luxury cars use it.
The V12 is perfectly balanced at 60 degrees. This is a fairly narrow V, and looks particularly tidy when accommodating a nice stack of Weber carburetors in the centre of the V- as done in many 50's and 60's Ferraris. This results in a tall engine and a hood scoop is generally needed to clear the air intakes -which looks fine in a pontoon fendered Testa Rossa.
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