Expert: Paul Wilczynski - 2/1/2009

Question
I've heard that "older" cars can't use the same engine oil as modern vehicles, something to do with their flat cam shafts, but you can purchase additives at speed shops to compensate. Any truth to that, and are my '70 TR6 or '93 Caprice considered "old"? Also, is it safe to use 10% ethanol fuels in the Triumph. I may not be able to find conventional gas much longer and I worry about fuel system damage..

Answer
Oliver:

The best advice I can give you regarding the use of additives in older engines, is that they're not necessary, except in certain cases.

How "old" your engine is depends upon mileage and use, not year of manufacture. The Triumph engine, for example, will be much more worn than the Caprice, even if they both show the same mileage--the engine's metallurgy is not up to 90s American standards, and also it has a much higher wear factor.

Among my many cars, I own a '95 Miata "M" Edition (Merlot), which is one of our daily drivers. This car is possibly the best-engineered small car of all time, considering its price and its vintage. It's not unusual to see one of these little 1.8L engines run virtually maintenance-free for 250,000 miles or even more. Amazing, considering that at 80 MPH in 5th gear, this car is turning something like 3800 RPM, sometimes for many hours at a time.

Mine has 125,000 miles on the clock, and the valve train used to make a bit of noise in the morning for a few seconds if the car hasn't been driven for a few days. I have taken to adding a pint of good old STP Oil Treatment at each oil change (every 3-4K miles), for the past year and a half. I no longer have any noise.

So, an additive like STP can serve a purpose, but it's not a cure-all. If you've got some valve train noise (excluding timing chain noise!), try STP or something similar; if it works, fine!

Regarding the ethanol question, the 175CD Stromberg carbs used on your TR6, may have rubber parts (including that big old piston diaphragm!) which use formulas not known for longevity when in the presence of ethanol. You need Buna-N seals and diaphragms, not natural rubber.

Here's my tip: If you don't know what type of rubber is in the seals already in your carbs, pick up a couple of rebuild kits which contain diaphragms. Seals of recent manufacture will be made of Buna-N, which is ethanol-resistant.

Store these away in a sealed Tupperware container to keep them from the air. Should your carbs show signs of deterioration after a year or two running on the ethanol blend, open them up and check the rubber parts. Replace as needed. Eventually somebody's going to reformulate the rubber in these parts (if they haven't already) to make them ethanol-resistant.

Note also that ethanol attacks cork gaskets (because of the natural rubber binder used in these) and leather seals, so you should replace any of these materials which may be in your fuel system, with a suitable alternate material.

Hope that this helps!

--Paul