just to let you guys know.
I just did first step to full synthetic, with 3500 miles on I just pumped out (3/4 quart)of castrol 10-30 from the engine and I added 5-20 synthetic Amsoil in the same amout. I had my dealer change my oil at 1400 miles first time. It did not look good and engine felt strianed.
Second time Castrol after only 2000 miles was dark and tick and engine started to feel strained and lazy again.
My stop and go Florida traffic with A/C on does not do any good for the engine. P5's engine when still cold sounds awfull, like a truck with loose valves, this Amsoil addition really made it less buzy and strain.
Now after swaping part of oil for Amsoil it feels quite a bit less strained, I get better cold starts (less noisy) and engine rev's up quicker, also engine feels more relaxed now.
What a difference good synthetic can make.
At 4500 I will add Full quart of Amsoil and rest (2.6 quarts)Pennzoil 5-30 for another 3000 miles and finally at 7500 my engine will see 100% synthetic oil change.

 

That's very interesting... doing a step upgrade to synthetic. I've never heard anyone do that before but it does seems like a good idea.

But, when you mix engine oils, shouldn't you try to use the same viscosity? that means if you had regular 10w30 in it, you should add in synthetic 10w30. Anyone care to clarify this?

 

You're kidding, right???

The reason that you shouldn't mix oils is that the different weights might degrade the performance of the base oils. Oil tends to mix pretty well. Lighter oil will NOT stay separate from heavier oil. It's not like oil and water (which will mix in an engine. If you've ever blown a head gasket, you know this to be true).

 

I will get it changed completely in next 600 miles, synthetic will also clean the engine (break-in period really kills oil quick)before switching to "all good stuff".
I'm not the first one doing switch to synthetic in steps.
I've tried Pennzoil with Amsoil
mix 3:1 and it worked great for 6000 miles on my previous car, that mix did not make my engine feel strain and lazy like reg. Castrol did after 2000 miles. I'm driving in a lot of traffic and A/C on with some cold mornings, it's very tough on the engine.
It can be a great cost effective alternative to full synthetic.
Friend of mine does Mobil1 with Pennzoil and it works great for years now.

 

Honestly, youre doing more harm than good to your engine by NOT switching right now to synthetic. If you switched right now to synthetic you know what would happen? You'd get slightly better gas mileage (less friction), you'd have LESS wear and tear on the engine and your engine will be more quiet on cold starts.

If you keep running castrol (which is pure ***** IMHO), you runt he risk of further wear and tear on your engine and problems maybe down the road.

I'll tell you this. my previous car wasa 99' Civic Si that had the high revvin' B16A2 engine that revved to an atmospheric 8,000 rpms. I used Mobil 1 from 600 miles to 40,000 miles (when i got rid of the car) and I never heard one odd sound, no valve train noise on cold startups, and virtually NO wear and tear on the valvetrain. And that was with revving daily, no make that hourly or more to redline 8Krpms.

there were also one other occasion where i was simply too busy to change my oil (kept planning on it and was getting ready for my wedding,). Well... for 5K miles I let the change go all the while revving the **** out of it.

i checked the dipstick one day and holy *****, there was NO oil registering!! still, i inspected the valvetrain and not on scoring mark was noted. Even though i was almost 2 quarts low! synthetic is the ONLY way to go. just stay way clear of any castrol product.

 

Good to hear SilPro5, I just gave my dealer four bottles of Mobil 1 Trisynthetic 10W-30 and he gave me back one of them, guess where the other three are hehe

Can't tell you if there's any difference yet, too early to tell, but I'll let you know after tomorrow morning........

 

The engines must be fully broken-in to switch to synthetic, and if you will not let it break-in it will take forever with more lubricating and wear protecting Synthetic.
Don't belive that engine will fully brake-in after 600 miles, it takes at least 5000 miles.
Synthetic does slow down necessary wear in the engine during break-in period. Later when the engine is fully broken-in Synthetic protects it from further wear, overheating, by providing much better lubrication and heat transfer, and longevity, what makes it so much better than reg. oils.
I added a little synthetic now (after 3600 miles) so the engine will stay clean (all that sludge and metal particles during break-in)and I will slowly increase amount of synthetic to fianally switch over at around 7500 miles.
It just makes more sence to me.

 

This might help
Break-in

and this

Mobil 1

Look in the Why synthetics area

 

I use to have 2 ZX3's both with the same Zetec 2.0 liter engines that are very similiar to our 2.0 in P5.
First one I did pre-mature switch over to synthetic at 3000 miles and it took so long for that engine to losen-up and wear-in (break-in).
With my second ZX3 I did the same thing that I'm doing now with P5 (full synthetic after 7500 miles).
Those two felt like two different engines, at 10K miles my first zx3 was still tight and hated to be reved-up, it still felt kinda lazy and noisy when pushed.
Second ZX3 at 10K was just much more relaxed and less strained when pushed it almost felt more powerfull.
It was the best way of checking and confirming when to switch.
I tried Amsoil and Mobil1, Amsoil is smoother than very good Mobil1.