Switching oils and extending drains

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Staff member
May 27, 2002
Guelph, Ontario
I was wondering exactly what happens when you switch brands of oil and go immediately to extended drains with it. I've always told people it's not good to do this, but a recent 24k Amsoil analysis that was posted here showed pretty good results for a first interval. Generally speaking doesn't the TBN drop faster and oxidation go up more on the first interval with a different oil? Also, what about if the change is from one synthetic to another? (as opposed to being from dino to synthetic) My sister's car for instance, is now running TriSynthetic (the rare SL formulation) and in the spring I am going to switch it over to SuperSyn. My sister drives the wheels off her 99 Civic, in the three weeks since I changed her oil she put on 1300 miles. So she racks em up fast! I was figuring when I switch her over to SuperSyn that I would only let that first batch go 6k, and then let the second interval with it go much longer, to about 12k. But what if I just start right away with the SuperSyn at 12k in her car? (keeping in mind that she does almost all highway driving, very long trips every day to work and back plus long trips on the weekends-she's a snowboarder and mountain biker so she travels far away a lot) A little more history here. Her car had about 33k on it when she bought it, and up to that point it had always had 3k oil changes at the Honda dealer with their bulk 5w30. So her current run of TriSynthetic is the very first interval on a synthetic oil. I'm also wondering if I should get her to spring the extra $$$ for a $14 K&N oil filter for her extended intervals, or go with a $4 AC Delco PF1127. I'd prefer not to have to change the oil filter at all during that 12k interval (which would probably only take her 6 months to acheive) Yes, it's decisions like these which keep me awake at night. [Smile] [ December 13, 2002, 06:44 AM: Message edited by: Patman ]
I personally like a medium run before going long. Yes there are outliers on both sides. But wisdom says, especially on a well broken in car - when changing over - just do a 3-5K interval with your choice of synthetic oil. I think this REALLY applies if you used ANY type of flush... [ December 13, 2002, 07:08 AM: Message edited by: Pablo ]
On the new cars I have owned I just go to extended drains of 12,000 at the time of change over. On the 3 or 4 I have converted I go 3-4k do a change and analysis and go from there. I haven't seen much diff but it depends on whether the engine being converted was cared for. In the future if I buy a used car I will clean with Neutra for 500 miles then convert. I am also going to start using Schaeffers blend in two cars at the next changes due to the great reuslts people on this board are having with it.
I'm definitely going to be doing analysis on each oil change with her car, so I guess I will see how the first numbers look on the first 5-6k interval with TriSynthetic. If it looks to be pretty good, like it could've gone a lot longer, then maybe the first interval with SuperSyn I'll push it longer. Otherwise I will do another 5-6k interval with SuperSyn and then go to the 12k interval.
Before I made that 24K mile run on the same oil, I drained the previous oil, then refilled with some Chevron Supreme, a new cheap filter, and a can of Amsoil Engine Flush. I then followed the instructions on the can. Funny this is, the oil that was run with the flush didn’t come out too dirty. For the prior 10-15 K miles, I was running Delo 15W-40 conventional at 3K mile change intervals. Now, this stuff really blackened up during 3K miles. I think the heavy duty detergents in the Delo really cleaned up the motor. Regarding the Amsoil Engine Flush, I think this is a great product. It is not a harsh solvent like Gunk or K&W. Just lots of detergent. In an old 740 Volvo, I used it with the same methodology, new oil—can of flush, etc., and the stuff that drained out was simply amazing.
Well, if you change the present batch at say 6K, I think you should have a clearer idea of how long to run the SS. We know that the SS is better (although not dramatically) than the TriSynso so you will be conservative with the SS. As far as filters go-thats a tough one. I personally can't see keeping even the K&N in more than about 8 or 9K miles or so. [freaknout] I assume the Civic is a horiszontal filter [Confused] So the anti-drainback valve may be shot by then [crushedcar] . It just may make economic sense not using a K&N and just changing filters at the 6K mark. Assuming the Mobil can handle the full 12K it may just make sense going with a cheaper filter and changing during the 12K. If you have to get under the car or have to jack it up to get to the filter [Eek!] -I vote to change the oil maybe every 8-9K miles with the K&N filter at the same time. Like I said-this oil sample will clear things up. Until then-try to get some sleep Patman [Big Grin]
Her car uses a horizontal filter, and I can reach it from above pretty easily so it's not too hard to change, so I may just go with an AC Delco and change it once halfway through. I still wonder if any of us come anywhere close to clogging up a filter, even with 10k + intervals. If the wear metals are low then I just wonder how the filter is going to be full. I sure wish there was some easy way to tell when a filter was full so we'd have some sort of idea. Many of us are worried about filters getting full when in reality we might be worried over nothing. [I dont know]
Well, I can tell you what I was comfortable with, but I don't have any analysis to back it up. When I bought my '90 Saab it had 113k mi on it. I knew from (non)maintenance records & discussions with servicing mechanics that the previous owner had been very lax in oil changes, sometimes going 7k-9k mi on bulk dino oil. At the time I was a dyed-in-the-wool Castrol fan, so I gave it GTX 10W-30 every 3k mi up to 120k. Between those two mileage points I'd been torturing myself over switching to full syn, & finally decided I'd had enough. (How's that song go? "I've got a Jihad in my head & I want you all to come!") So anyway, I decided to just do it. I started 10k mi intervals on Syntec 10W-30, using standard ACDelco DuraGuard filters. I think I had a brief lapse & changed the first filter after 5k mi, but ever since it's been only at the oil changes. At some point I felt the Pure Ones were a better choice than the ACDs, but now I flip-flop between the two. I've also switched to Mobil 1. My Saab's now got over 160k mi on it & it's still doing fine mechanically. My preferred interval of 10k mi is purely for my own convenience; I don't want to remember mileage numbers any more. (What can I say? I'm a base-10 kinda guy!) At the time I was putting about 15k mi/yr on my car, & my wife was putting about 8k mi/yr on hers, so 10k intervals works for me. You know you're going to be sampling anyway, & you know that what you're switching to is better than what's been used previously. Why not go the distance & use it as another data point? If you get concerned about it, change filters while you're taking samples & top up with close a full new quart of SS. That should be more than enough for the type of driving she does. Now repeat after me, "Ohwah Tagoo Siam" Okay, faster... faster...
Originally posted by Greg Netzner: Now repeat after me, "Ohwah Tagoo Siam" Okay, faster... faster...
Don't repeat this one faster and faster... "Awah Tana Siam"
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