My opinion, not make a difference.
Understand that "synthetic" can mean many things, including Group 3 synthetic which is just a further-processed mineral oil, and group 4/5 PAO's and Esthers. The group 3 oils certainly have advantages over group 1 and 2 conventional oils, like a lower volatility, higher viscosity index... etc... but they have no cleaning advantage over just a straight conventional. Most of the less expensive "synthetics" are of this base stock, or a blend of it and some group 4/5. That's not to say they couldn't have some additive to do more cleaning, and I'm sure many do, my point is that the term "synthetic" in the US is a pretty vague one and there isn't a huge difference between a cheap synthetic and a good dino anymore. With API spec SN coming this fall the gap will narrow even further. Really, what I would look for would be a high mileage oil where you would be assured enhanced cleaning ability, and you could definitely get a synthetic or synthetic blend if that's what you wanted.
Really, what the concern might be is that using a higher detergent oil would be cleaning the valve guide seals of whatever deposits they have on them and actually increasing oil consumption. The risk of this, and even if it was a guarantee, IMO is outweighed by the fact you need to get this engine clean especially considering it's history of being sludge prone.
So if it were mine I would, at the very least, change over to a High Mileage oil and perhaps a synthetic at that. You might also do some reading/searching over at bobistheoilguy.com/forums and see if you're interested in using something like autorx that might clean more aggressively.
There's nothing special about Toyota OEM oil, besides their 0w-20 which is fantastic but expensive.
Have you considered pulling a valve cover to see how bad things are?
Understand that "synthetic" can mean many things, including Group 3 synthetic which is just a further-processed mineral oil, and group 4/5 PAO's and Esthers. The group 3 oils certainly have advantages over group 1 and 2 conventional oils, like a lower volatility, higher viscosity index... etc... but they have no cleaning advantage over just a straight conventional. Most of the less expensive "synthetics" are of this base stock, or a blend of it and some group 4/5. That's not to say they couldn't have some additive to do more cleaning, and I'm sure many do, my point is that the term "synthetic" in the US is a pretty vague one and there isn't a huge difference between a cheap synthetic and a good dino anymore. With API spec SN coming this fall the gap will narrow even further. Really, what I would look for would be a high mileage oil where you would be assured enhanced cleaning ability, and you could definitely get a synthetic or synthetic blend if that's what you wanted.
Really, what the concern might be is that using a higher detergent oil would be cleaning the valve guide seals of whatever deposits they have on them and actually increasing oil consumption. The risk of this, and even if it was a guarantee, IMO is outweighed by the fact you need to get this engine clean especially considering it's history of being sludge prone.
So if it were mine I would, at the very least, change over to a High Mileage oil and perhaps a synthetic at that. You might also do some reading/searching over at bobistheoilguy.com/forums and see if you're interested in using something like autorx that might clean more aggressively.
There's nothing special about Toyota OEM oil, besides their 0w-20 which is fantastic but expensive.
Have you considered pulling a valve cover to see how bad things are?
