Nothing generates more debate (other than timing belt change intervals) in the 308 world than the simple question of what oil to use. The simple consumables that we need to keep our cars healthy and happy are not as complicated as you might imagine. The car is exotic, the oil that goes in the engine isn't. This page is dedicated to providing Ferrari 308 owners with solid advice on consumables.
1. Engine Oil
I have put this one first because it is so often the subject of debate in on-line discussions that it has become a bit of a joke. The 308 owner's manual calls for 10W-50 oil. In the mid-1970s, synthetic oils were not commonly used in cars yet, so the oil was a "dino" oil. To my knowledge there are no oils made that are exactly what Ferrari specified originally. Given that these cars are going to have their oil changed regularly and they are rarely driven a lot of miles on the oil or driven when its particularly cold out, the specific oil you put in your 308 is probably not as important as you think. The most important thing is that the oil have ZDDP. This is a wear-reducing additive that has been phased out in most oils because of its poor environmental characteristics. But many classic cars with certain cam/flat tappets/buckets & followers were designed during the "ZDDP era" will experience higher than normal wear if you use an oil without ZDDP. The following oils are popular (and perfectly fine) in a 308 engine:
• Castrol 5W-50 Syntec
• Valvoline VR-1 20W-50 (recommended by Ferrari Guru David Feinberg at FSoB for older 308s)
• Pennzoil Ultra Euro 5W-40 (recommended by Ferrari Guru David Feinberg at FSoB for 308 QV)
• Redline 5W-40
This is by no means a complete list of acceptable motor oils for the 308, but a list generated by experts as preferable and widely available. And you will note they are mostly all synthetic. Please, stop worrying about dino versus synthetic. The 5W oils will be better for start-up wear in cold weather, but let's be honest--how many times are we driving our 308s in the winter?
It is important that you understand that the compression ratio of the 308 is only about 8.8:1, which means that detonation is not a problem with any commercially available gasoline. If you don't understand octane ratings, read about it. Basically octane is a measurement of a fuel's resistance to detonation. A diesel engine works without spark plugs because it has a very high compression ratio. When the piston compresses the fuel/air mixture, it gets so hot that it "detonates" by itself. In a gasoline engine, spark plugs are used to ignite the mixture at the exact right moment, and that moment is a different place in the rotation of the engine depending on how fast the engine is turning (this is the "spark advance"). If the mixture is doing its own thing without regard to the spark plug like a diesel, that's a problem.
The higher the compression ratio of an engine, the more power you can get out of a given displacement, but the more prone the engine will be to detonation. So, you need higher octane fuels to suppress that tendency to detonate. Modern engines make more power with less displacement, but they do it in part with high compression, which is why so many modern high performance engines require 93 octane fuel. Perhaps because of this, people often seem to be of the impression that higher octane fuels somehow possess more "energy." Not so. High octane fuels just have more additives to supress detonation--so they charge more for it.
With an 8.8:1 compression ratio, the 308 has a very modest compression ratio and it's simply not going to knock. You can put 87 octane gas in it. You do not need 93--that is a total waste of money. If you want to put 93 in it, go right ahead, it won't hurt anything, but the car will not perform any better. Just to compare, modern cars often have more like 12:1 compression ratios.
3. Transaxle Oil
Unlike most cars which have a differential seperate from the transmission, the 308 has a combined limited-slip differential/transmission ("transaxle"). As a result, it tends to be a bit finicky about the oil in it because the oil is trying to be two different things at once: a limited-slip differential oil, and a transmission oil.
Put the wrong oil in the transaxle and it might shift great but the limited-slip diff can "chatter" (meaning it won't slip quite enough in tight turns and you can literally feel the car "jumping" as it tries to allow one rear wheel to spin faster than the other.) Get the oil right for the differential to work right and it might not shift well, especially cold. Most experts agree that there are two oils that work best in the 308 and in my opinion these are the only two that should go in your car. I use Redline 75W90 NS as it has always been great for me. (Some people prefer the regular 75W90 that contains the slip modifier.) The Royal Purple is every bit as good. They are both expensive, and worth every penny. They used to be hard to find, but Amazon delivers them right to your door.
• Redline 75W90 or Redline 75W90
NS ("No Slip Modifier")
• Royal Purple 75W90 MaxGear
4. Oil Filter
Many different oil filters will actually fit the car and function. However the proper oil filter has a center standpipe and an anti-drainback valve in it. You can buy a UFI which is fine but overpriced, a Fram which is a POS and may or may not have the right internals. But the best oil filter for the 308 without question is the Baldwin B253, available at any local truck supply place. Not only does it have the right internals and only costs $15 or so, it is red. You can't go wrong. Trust me on this one. (If you don't want to trust me, check out this thread on fchat for a few pictures of the collapsed internals of Fram oil filters. Fram filters are garbage and have no place on a Ferrari.)
5. Spark Plugs
For years, the go-to plugs for the 308 were plain old NGK BP5ES or BP6ES but in recent years I have been running NGK Iridium BPR6EIX on the recommendation of David Feinberg of
FSoB and I have to tell you...new technology is a good thing. I would never go back to the old school plugs in a million years. Iridium are worth every penny. The car starts better, idles better and the plugs foul far less. Hotter spark, cooler electrode, simple as that.
(This article is a work in progress. If you have suggestions on other consumables for this article please drop me a line!)