diff --git a/src/problems/nonlinear_problems.jl b/src/problems/nonlinear_problems.jl
index 78a6e05ef..971173f5c 100644
--- a/src/problems/nonlinear_problems.jl
+++ b/src/problems/nonlinear_problems.jl
@@ -104,6 +104,9 @@ function IntervalNonlinearProblem(f, tspan, p = NullParameters(); kwargs...)
     IntervalNonlinearProblem(IntervalNonlinearFunction(f), tspan, p; kwargs...)
 end
 
+
+_default_nl_specialize(p) = sizeof(p)==0 || ismutable(p) ? AutoSpecialize : FullSpecialize
+
 @doc doc"""
 
 Defines a nonlinear system problem.
@@ -183,7 +186,7 @@ mutable struct NonlinearProblem{uType, isinplace, P, F, K, PT} <:
     This is determined automatically, but not inferred.
     """
     function NonlinearProblem{iip}(f, u0, p = NullParameters(); kwargs...) where {iip}
-        NonlinearProblem{iip}(NonlinearFunction{iip}(f), u0, p; kwargs...)
+        NonlinearProblem{iip}(NonlinearFunction{iip, _default_nl_specialize(p)}(f), u0, p; kwargs...)
     end
 end
 
@@ -198,7 +201,9 @@ function NonlinearProblem(f::AbstractNonlinearFunction, u0, p = NullParameters()
 end
 
 function NonlinearProblem(f, u0, p = NullParameters(); kwargs...)
-    NonlinearProblem(NonlinearFunction(f), u0, p; kwargs...)
+    iip = isinplace(f, 3)
+
+    NonlinearProblem(NonlinearFunction{iip, _default_nl_specialize(p)}(f), u0, p; kwargs...)
 end
 
 """
diff --git a/src/scimlfunctions.jl b/src/scimlfunctions.jl
index 239791d61..cc02213df 100644
--- a/src/scimlfunctions.jl
+++ b/src/scimlfunctions.jl
@@ -1724,19 +1724,16 @@ For more details on this argument, see the ODEFunction documentation.
 
 The fields of the NonlinearFunction type directly match the names of the inputs.
 """
-struct NonlinearFunction{iip, specialize, F, TMM, Ta, Tt, TJ, JVP, VJP, JP, SP, TW, TWt,
+struct NonlinearFunction{iip, specialize, F, TMM, Ta, TJ, JVP, VJP, JP, SP,
     TPJ, O, TCV, SYS, RP, ID} <: AbstractNonlinearFunction{iip}
     f::F
     mass_matrix::TMM
     analytic::Ta
-    tgrad::Tt
     jac::TJ
     jvp::JVP
     vjp::VJP
     jac_prototype::JP
     sparsity::SP
-    Wfact::TW
-    Wfact_t::TWt
     paramjac::TPJ
     observed::O
     colorvec::TCV
@@ -3801,23 +3798,17 @@ end
 SDDEFunction(f::SDDEFunction; kwargs...) = f
 
 function NonlinearFunction{iip, specialize}(f;
-        mass_matrix = __has_mass_matrix(f) ?
-                      f.mass_matrix :
-                      I,
-        analytic = __has_analytic(f) ? f.analytic :
+        mass_matrix = __has_mass_matrix(f) ? f.mass_matrix : I,
+        analytic = __has_analytic(f) ? Void(f.analytic) :
                    nothing,
-        tgrad = __has_tgrad(f) ? f.tgrad : nothing,
-        jac = __has_jac(f) ? f.jac : nothing,
-        jvp = __has_jvp(f) ? f.jvp : nothing,
-        vjp = __has_vjp(f) ? f.vjp : nothing,
+        jac = __has_jac(f) ? Void(f.jac) : nothing,
+        jvp = __has_jvp(f) ? Void(f.jvp) : nothing,
+        vjp = __has_vjp(f) ? Void(f.vjp) : nothing,
         jac_prototype = __has_jac_prototype(f) ?
                         f.jac_prototype : nothing,
         sparsity = __has_sparsity(f) ? f.sparsity :
                    jac_prototype,
-        Wfact = __has_Wfact(f) ? f.Wfact : nothing,
-        Wfact_t = __has_Wfact_t(f) ? f.Wfact_t :
-                  nothing,
-        paramjac = __has_paramjac(f) ? f.paramjac :
+        paramjac = __has_paramjac(f) ? Void(f.paramjac) :
                    nothing,
         syms = nothing,
         paramsyms = nothing,
@@ -3864,40 +3855,51 @@ function NonlinearFunction{iip, specialize}(f;
     sys = sys_or_symbolcache(sys, syms, paramsyms)
     if specialize === NoSpecialize
         NonlinearFunction{iip, specialize,
+            Any, Any, Any, Any,
             Any, Any, Any, Any, Any,
-            Any, Any, Any, Any, Any,
-            Any, Any, Any,
+            Any,
             typeof(_colorvec), Any, Any, Any}(_f, mass_matrix,
-            analytic, tgrad, jac,
+            analytic, jac,
             jvp, vjp,
             jac_prototype,
-            sparsity, Wfact,
-            Wfact_t, paramjac,
+            sparsity, paramjac,
             observed,
             _colorvec, sys, resid_prototype, initialization_data)
+    elseif specialize === AutoSpecialize && iip
+        NonlinearFunction{iip, specialize,
+            Void, typeof(mass_matrix),
+            analytic isa Void ? Void : typeof(analytic),
+            jac isa Void ? Void : typeof(jac),
+            jvp isa Void ? Void : typeof(jvp),
+            vjp isa Void ? Void : typeof(vjp),
+            typeof(jac_prototype),
+            typeof(sparsity), typeof(paramjac),
+            observed isa Void ? Void : typeof(observed),
+            typeof(_colorvec), typeof(sys), typeof(resid_prototype),
+            typeof(initialization_data)}(Void(_f), mass_matrix,
+            analytic, jac,
+            jvp, vjp, jac_prototype, sparsity, paramjac,
+            observed, _colorvec, sys, resid_prototype, initialization_data)
     else
         NonlinearFunction{iip, specialize,
-            typeof(_f), typeof(mass_matrix), typeof(analytic), typeof(tgrad),
+            typeof(_f), typeof(mass_matrix), typeof(analytic),
             typeof(jac), typeof(jvp), typeof(vjp), typeof(jac_prototype),
-            typeof(sparsity), typeof(Wfact),
-            typeof(Wfact_t), typeof(paramjac),
+            typeof(sparsity), typeof(paramjac),
             typeof(observed),
             typeof(_colorvec), typeof(sys), typeof(resid_prototype),
             typeof(initialization_data)}(_f, mass_matrix,
-            analytic, tgrad, jac,
-            jvp, vjp, jac_prototype, sparsity,
-            Wfact,
-            Wfact_t, paramjac,
+            analytic, jac,
+            jvp, vjp, jac_prototype, sparsity, paramjac,
             observed, _colorvec, sys, resid_prototype, initialization_data)
     end
 end
 
 function NonlinearFunction{iip}(f; kwargs...) where {iip}
-    NonlinearFunction{iip, FullSpecialize}(f; kwargs...)
+    NonlinearFunction{iip, AutoSpecialize}(f; kwargs...)
 end
 NonlinearFunction{iip}(f::NonlinearFunction; kwargs...) where {iip} = f
 function NonlinearFunction(f; kwargs...)
-    NonlinearFunction{isinplace(f, 3), FullSpecialize}(f; kwargs...)
+    NonlinearFunction{isinplace(f, 3), AutoSpecialize}(f; kwargs...)
 end
 NonlinearFunction(f::NonlinearFunction; kwargs...) = f