I'd personally stay within the factory oil specs noted in the manual, if not very close to it.
With regards to using a much thicker oil like a 15W-50
Anyways, sure, a thicker oil will have the ability to better protect then a thinner one, but it's not just about thin vs thick oil here. We have other things to consider, like; tolerances, friction, flow, temps,..etc. That oil has to flow inside the engine and increasing the viscosity increases friction. The heavier the oil, the harder time flowing. You'll get a more sluggish engine, increased internal temp/more friction, decreased MPG,..etc. I just don't understand why people are so eager to dump an oil in their engine that is much heavier then what the manufacturer states. Engine oil temps are only going to get so high, even with increased ambient temps. I don't claim to be an oil expert, but it doesn't always make complete sense to just throw a higher viscosity oil into an engine, especially a 1.8t.
I have driven 1.8/t's since '85 and have driven them like public race cars in SoCal 98% of the time (high rev shifts, up and down shifting, high speeds, sitting in 3rd/4th gear w/ high revs,...etc. red line, red line,.. red line), and this for extended times while driving 100's of miles. If that isn't "hard driving" then I don't know what is. You may race/track, but it's for what, a 1/2 hour or less perhaps? I can take my car out for a drive and be just as abusive in most cases.
During my time with these VW/Audi 1.8/t's, I have kept within the recommended oil; 5W-30/40, 10W-30/40, 0W-40). IMO, the 5W-40 seemed to be the best suited for the 1.8t, my climate and driving habits. I ran Red Line oils for 8 years and recently switched to Motul. I run their 300V 5W-40 in my '03 Audi A4 1.8t (29K miles) and their 8100 Ester E-Tech 0W-40 in my '00 VW 1.8t (66K miles). Before this, I had an '85 Gti which was my most street abused car. I had almost 300K miles on that engine and drove it to **** and back. It was never rebuilt in that time. I also have done extended drains for 8 years, averaging 8-12 miles OCI's. ( I should also note that I have used the Mecca Performance filter during this time also).
The 1.8t is a proven little engine and can last, even with more then normal use [abuse]. Stick with the same viscosity recommended for your vehicle, or very close to it. I'd use Motul myself and probably their 5W-40 or 0W-40 as mentioned above.
BTW; don't Honda's have some of the tightest tolerances and specify xW-20 oil viscosity? I can't believe a 15W-50 would be good for it.
